javascript get current function name in strict mode

Can I get the name of the currently running function in JavaScript? Is there a weapon that has the heavy property and the finesse property (or could this be obtained)? Strict mode makes it easier to write secure JavaScript. It disables features that are confusing or poorly thought out. Strict mode makes it easier to write "secure" JavaScript. Where NUMBER is the amount of jumps you want to do to the past (Number = 1 => first parent) For a sloppy mode function, this is always an object: either the provided object, if called with an object-valued this; or the boxed value of this, if called with a primitive as this; or the global object, if called with undefined or null as this. How to get function name in strict mode [proper way], stackoverflow.com/questions/618820/logging-vs-debugging/. In sloppy mode, assigning to NaN does nothing; the developer receives no failure feedback. Strict mode eliminates some JavaScript silent errors by changing them to throw errors. Note: Using Function.caller is non-standard and arguments.callee is forbidden in strict mode. // Strict mode syntax for entire script. Its possible that you are approaching the problem wrong. Trying to get f.[[Prototype]].caller", // caller is an own property with descriptor {value: null, writable: false, enumerable: false, configurable: false}, // f doesn't have an own property named caller. stack trace to the console. Content Discovery initiative April 13 update: Related questions using a Review our technical responses for the 2023 Developer Survey. Generic Doubly-Linked-Lists C implementation. Maybe if you explain what you're trying to do more broadly the community can propose alternatives. // So codes below the line 'use strict' will be executed in strict mode. In sloppy mode, a function declaration inside a block may be visible outside the block and even callable. A leading-zero syntax for the octal is rarely useful and can be mistakenly used, so strict mode makes it a syntax error: The standardized way to denote octal literals is via the 0o prefix. "boxed"). How to append HTML code to a div using JavaScript ? How about saving the world? Approach 1: Using arguments.callee method: It refers to the currently executing function inside the function body of that function. Was Stephen Hawking's explanation of Hawking Radiation in "A Brief History of Time" not entirely accurate? Certain language functions are so pervasive that performing runtime checks has a considerable performance cost. Generic Doubly-Linked-Lists C implementation. This use case is weak: name the enclosing function! Strict mode makes it impossible to accidentally create global variables. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. How about saving the world? Example 2: This example display currently running function using console.log method. Connect and share knowledge within a single location that is structured and easy to search. acknowledge that you have read and understood our, Data Structure & Algorithm Classes (Live), Data Structures & Algorithms in JavaScript, Data Structure & Algorithm-Self Paced(C++/JAVA), Full Stack Development with React & Node JS(Live), Android App Development with Kotlin(Live), Python Backend Development with Django(Live), DevOps Engineering - Planning to Production, GATE CS Original Papers and Official Keys, ISRO CS Original Papers and Official Keys, ISRO CS Syllabus for Scientist/Engineer Exam, JavaScript Importing and Exporting Modules, Javascript Error and Exceptional Handling With Examples, Introduction to Object Oriented Programming in JavaScript, Creating objects in JavaScript (4 Different Ways). Not the answer you're looking for? JavaScript program has no side effects. On whose turn does the fright from a terror dive end? How to change the background color after clicking the button in JavaScript . In strict mode you can no longer reference callee (see the related discussion at Javascript: is the arguments array deprecated?) Note: In strict mode, accessing caller of a function throws an error the API is removed with no replacement. How to use strict mode: Strict mode can be used in two ways, remember strict mode doesn't work with block statements enclosed in {} braces. In sloppy mode, function calls like f() would pass the global object as the this value. However, it was so intuitive that most browsers implemented it as an extension grammar. Creating Error object for each calling is just a hack, not a working method. You can use strict mode in all your programs. Create function: After that whenever you need, you simply use: Warning: The 5th edition of ECMAScript (ES5) forbids use of arguments.callee() in strict mode. How to Make Dark Mode for Websites using HTML CSS & JavaScript ? delete name in strict mode is a syntax error: If the name is a configurable global property, prefix it with globalThis to delete it. var functionName = function() {} vs function functionName() {}. Which was the first Sci-Fi story to predict obnoxious "robo calls"? Is there any plans to make module standard for nodejs? const newStack = stack.split("\n").slice(NUMBER).join("\n"); There's a (long) discussion here about it: http://groups.google.com/group/comp.lang.javascript/browse_frm/thread/b85dfb2f2006c9f0. Get current function name in strict mode I need the current function name as a string to log to our log facility. Use //# instead, TypeError: can't assign to property "x" on "y": not an object, TypeError: can't convert BigInt to number, TypeError: can't define property "x": "obj" is not extensible, TypeError: can't delete non-configurable array element, TypeError: can't redefine non-configurable property "x", TypeError: cannot use 'in' operator to search for 'x' in 'y', TypeError: invalid 'instanceof' operand 'x', TypeError: invalid Array.prototype.sort argument, TypeError: invalid assignment to const "x", TypeError: property "x" is non-configurable and can't be deleted, TypeError: Reduce of empty array with no initial value, TypeError: setting getter-only property "x", TypeError: X.prototype.y called on incompatible type, Warning: -file- is being assigned a //# sourceMappingURL, but already has one, Warning: unreachable code after return statement. Fortunately, this careful review can be done gradually down the function granularity. Then the answer is there is none, which is why I asked for clarification. Word order in a sentence with two clauses, Embedded hyperlinks in a thesis or research paper, English version of Russian proverb "The hedgehogs got pricked, cried, but continued to eat the cactus". To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Using a variable, without declaring it, is not allowed: Using an object, without declaring it, is not allowed: Deleting a variable (or object) is not allowed. Fixes mistakes that make it difficult for JavaScript engines to perform optimizations: strict mode code can sometimes be made to run faster than identical code that's not strict mode. variables in the scope from which it was called. If the function f was invoked by the top-level code, the value of f.caller is null; otherwise it's the function that called f. If the function that called f is a strict mode function, the value of f.caller is also null. Strict mode code and non-strict mode code can coexist, so scripts can opt into strict mode incrementally. Use of reserved keywords as variable or function name. JavaScript was designed to be easy for novice developers, and sometimes it gives operations which should be errors non-error semantics. Actually, actually paying more attention to your question, it sounds like you might want the extra junk :), This worked for me but I think there's a typo in your regexp. Fixes mistakes that make it difficult for JavaScript engines to perform optimizations: strict mode code can sometimes be made to run faster than identical code that's not strict mode. In sloppy mode, a number beginning with a 0, such as 0644, is interpreted as an octal number (0644 === 420), if all digits are smaller than 8. It is possible to change each file individually and even to transition code to strict mode down to the function granularity. In ES5 and above, there is no access to that information. In this article i will introduce you to one of the most confusing and common doubt for every newbie devs, Duplicate parameters in javascript functions. In normal code arguments.callee refers to the enclosing function. It's surprising nobody else has pointed that out in the almost 3 years this answer has been here :-). mode will return the global object (window): Keywords reserved for future JavaScript versions can NOT be used as variable Why did US v. Assange skip the court of appeal? Any reason not to use this in a debugging environment? All browser compatibility updates at a glance, Frequently asked questions about MDN Plus. You may have to parse the name though, as it will probably include some extra junk. @DanRandolph: In my opinion this was a good answer in 2010 but is now slightly out of date because the, Its pretty cool, but you don't get the function-name if you are within the function, It does'n work on Chrome Version 59.0.3071.115 (Official Build) (64-bit) for, It does'n work on Chrome Version 59.0.3071.115 (Official Build) (64-bit), printing, developer.mozilla.org/en/Core_JavaScript_1.5_Reference/, developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/, http://groups.google.com/group/comp.lang.javascript/browse_frm/thread/b85dfb2f2006c9f0. What is the difference between call and apply? // SyntaxError: "use strict" not allowed in function with default parameter, // because this is a module, I'm strict by default, // All code here is evaluated in strict mode, // TypeError, because test() is in strict mode, // Assuming no global variable mistypeVarible exists, // this line throws a ReferenceError due to the, // misspelling of "mistypeVariable" (lack of an "a"), // Assignment to a new property on a non-extensible object, // If this weren't strict mode, would this be const x, or, // would it instead be obj.x? acknowledge that you have read and understood our, Data Structure & Algorithm Classes (Live), Data Structures & Algorithms in JavaScript, Data Structure & Algorithm-Self Paced(C++/JAVA), Full Stack Development with React & Node JS(Live), Android App Development with Kotlin(Live), Python Backend Development with Django(Live), DevOps Engineering - Planning to Production, GATE CS Original Papers and Official Keys, ISRO CS Original Papers and Official Keys, ISRO CS Syllabus for Scientist/Engineer Exam, Inline HTML Helper HTML Helpers in ASP.NET MVC, Different Types of HTML Helpers in ASP.NET MVC. 565), Improving the copy in the close modal and post notices - 2023 edition, New blog post from our CEO Prashanth: Community is the future of AI. How to get the ID of the clicked button using JavaScript/jQuery ? How can one get the name and line of a function that called the current one? Note: Making code that used to error become non-errors is always considered backwards-compatible. arguments.callee will give you a reference to the calling function, not a function name in string. Asking for help, clarification, or responding to other answers. Using Strict mode for the entire script: To invoke strict mode for an entire script, put the exact statement use strict; (or use strict;) before any other statements. Both involve a considerable amount of magical behavior in sloppy mode: eval to add or remove bindings and to change binding values, and arguments syncing named arguments with its indexed properties. These differences are very subtle differences. Thanks for contributing an answer to Stack Overflow! An example of a function called in strict mode: Not the answer you're looking for? Connect and share knowledge within a single location that is structured and easy to search. BCD tables only load in the browser with JavaScript enabled. Strict mode makes several changes to normal JavaScript semantics: Strict mode applies to entire scripts or to individual functions. Let's understand all these usage and values of "this" in various contexts:What does "this" refers to when used in a method? Note that you shouldn't do this if you intend to use a minifier like Terser, which may change the function names. Has the cause of a rocket failure ever been mis-identified, such that another launch failed due to the same problem? Making statements based on opinion; back them up with references or personal experience. Using "use strict" in functions with rest, default, or destructured parameters is a syntax error. How to get the children of the $(this) selector? Examples might be simplified to improve reading and learning. In strict mode, eval creates variables only for the code being evaluated, so eval can't affect whether a name refers to an outer variable or some local variable: Whether the string passed to eval() is evaluated in strict mode depends on how eval() is invoked (direct eval or indirect eval). How to get variable name in annonymous function construnction var f = function(){}; How do I remove a property from a JavaScript object? Can I general this code to draw a regular polyhedron? Share Improve this answer Follow edited Dec 26, 2013 at 15:03 answered Jul 5, 2011 at 18:18 MD Sayem Ahmed 28.5k 27 111 178 Add a comment 6 changes converting mistakes into errors (as syntax errors or at runtime), changes simplifying how variable references are resolved, changes making it easier to write "secure" JavaScript. Why doesnt a Javascript return statement work when the return value is on a new line. of JavaScript. Asking for help, clarification, or responding to other answers. How do I make function decorators and chain them together? This isn't an official term, but be aware of it, just in case. Connect and share knowledge within a single location that is structured and easy to search. There may also be large incompatibilities between implementations and the behavior may change in the future. I still would like to have a way to reference the name of the current function just for the purposes of throw error messages with a context. It's a hack and relies on non-standard feature: Error.prototype.stack. The guides section is new and still under construction. Again, cannot use in "strict mode", e.g. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. rev2023.4.21.43403. stacktracey seems to work cross browser pretty well. In strict mode, it is now undefined. Although that assumes that no value with the same name will collide (a reasonable assumption in many cases, and not so reasonable in others). Note that the only behavior specified by the ECMAScript specification is that Function.prototype has an initial caller accessor that unconditionally throws a TypeError for any get or set request (known as a "poison pill accessor"), and that implementations are not allowed to change this semantic for any function except non-strict plain functions, in which case it must not have the value of a strict mode function. Strict mode changes previously accepted "bad syntax" into real errors. The guides area is designed to help developers learn to better interact with the date and time problem domain, and the Moment.js library. * isn't going to help. The arguments inside the error function refers to this method's own arguments object. Copy and paste console.debug(arguments.callee) is more convenient ( I do not need to repeat function name). How to add options to a select element using jQuery? In this method, we use arguments.callee to refer to the name of the function. Why does awk -F work for most letters, but not for the letter "t"? Used in global scope for the entire script. This is to prevent code from being able to "walk the stack", which both poses security risks and severely limits the possibility of optimizations like inlining and tail-call optimization. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. In normal JavaScript, a developer will not receive any error feedback assigning values to non-writable properties. was passed to each function. Strict mode requires that function parameter names be unique. The statement use strict; instructs the browser to use the Strict mode, which is a reduced and safer feature set of JavaScript. Strict mode makes great strides toward treating eval and arguments as keywords. rev2023.4.21.43403. Strict mode makes it easier to write "secure" JavaScript. Note though that it may fail if called from an anonymous function. 14. arguments.callee. See ; non-standard and not allowed in strict mode, developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/. Though, in some implementations you can simply get the name using arguments.callee.name. in strict mode): The syntax, for declaring strict mode, was designed to be compatible with How to get the function name under "use strict"? You would have to make sure you add that function name twice. function functionName (fun) { var ret = fun.toString (); ret = ret.substr ('function '.length); ret = ret.substr (0, ret.indexOf (' (')); return ret; } Note: Using Function.caller is non-standard and arguments.callee is forbidden in strict mode. arguments.callee will give you a reference to the calling function, not a function name in string. Can you still use Commanders Strike if the only attack available to forego is an attack against an ally? What does the power set mean in the construction of Von Neumann universe? In such case, inside myFunction the value of this is not the same as intanz anymore, but it will get the value of this from the global context, which in strict-mode is undefined instead of the global window object.. Well, it doesn't look very clear at the beginning, but with a short example it will be easier to understand. Parabolic, suborbital and ballistic trajectories all follow elliptic paths. Using Strict mode for a function: Likewise, to invoke strict mode for a function, put the exact statement use strict; (or use strict;) in the functions body before any other statements. Console.trace is too verbose and will produce multiple lines, when I need only function name. This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. Consider: function f(n) { g(n - 1); } function g(n) { if (n > 0) { f(n); } else { stop(); } } f(2); At the moment stop () is called the call stack will be: f (2) -> g (1) -> f (1) -> g (0) -> stop () JSLint is suddenly reporting: Use the function form of "use strict". In strict mode, the value is passed directly without conversion or replacement. object, will throw an error. Not be reassigned. How to get GET (query string) variables in Express.js on Node.js? rev2023.4.21.43403. But in case of an error handler the result would be the name of the error handler function, wouldn't it? Not only will it tell you which functions How to create a virtual ISO file from /dev/sr0. So for other coming here the answer is YES and you can just add this line: All parts of a class's body are strict mode code, including both class declarations and class expressions. The following code checks the value a function's caller property. script or a function. How to get the children of the $(this) selector? Call. What does "up to" mean in "is first up to launch"? Strict mode reserves some more names than sloppy mode, some of which are already used in the language, and some of which are reserved for the future to make future syntax extensions easier to implement. How to jQuery : Can I get the name of the currently running function in JavaScript? Javascript: is the arguments array deprecated? However, arguments.callee.name is only available from inside the function. An example to test the theory Obviously, there is no standard way that always works, so you should always provide a name that can be used if no other name is found. Note that in case of recursion, you can't reconstruct the call stack using this property. It returns the null value if the function is invoked from the top-level JavaScript code. You need something like this if you want the arguments of MyFunction(): You can't do better than reliably, since that function has almost nothing to do with the error handler: The error handler can very possibly have been created in another context entirely, one enclosing MyFunction, or passed into it etc. Strict mode can be enabled using some directives such as 'use strict'. changes anticipating future ECMAScript evolution. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Strict mode fixes mistakes that make it difficult for JavaScript engines to perform optimizations: strict mode code can sometimes be made to run faster than identical code thats not strict mode. If you try to elaborate on the underlying solution you are trying to build, we might be able to give suggestions. are deprecated, SyntaxError: "use strict" not allowed in function with non-simple parameters, SyntaxError: "x" is a reserved identifier, SyntaxError: a declaration in the head of a for-of loop can't have an initializer, SyntaxError: applying the 'delete' operator to an unqualified name is deprecated, SyntaxError: await is only valid in async functions, async generators and modules, SyntaxError: cannot use `? How to enforce strict null checks in TypeScript ? How to get JS class name from class, but not from instance? Using a global variable in this case provides you a workaround to this problem. Why typically people don't use biases in attention mechanism? As noted this applies only if your script uses "strict mode". Sometimes this fixes the immediate problem, but sometimes this creates worse problems in the future. Get the size of the screen, current web page and browser window. A-143, 9th Floor, Sovereign Corporate Tower, We use cookies to ensure you have the best browsing experience on our website. It's a Primitive select. Can you recommend some? How to find all inputs that don't have color name and appends text to the span next to it using jQuery ? Which one to choose? Both extensions are problematic for "secure" JavaScript because they allow "secured" code to access "privileged" functions and their (potentially unsecured) arguments. Difference between var and let in JavaScript, Convert a string to an integer in JavaScript. "use strict" is just a string, so IE 9 will not throw an error even if it does not understand it. Strict mode makes it easier to write "secure" JavaScript. This is the same answer you got before, just wrapped up in a nice module, and using some V8-specific APIs. But arguments.callee.name only works in loose mode. webpack: Module not found: Error: Cant resolve (with relative path). We use cookies to personalise content and ads, to provide social media features and to analyse our traffic. Learn more about bidirectional Unicode characters. Javascript: How can I get the name of a function? Some websites now provide ways for users to write JavaScript which will be run by the website on behalf of other users. Duplicate property names used to be considered a SyntaxError in strict mode. Enable JavaScript to view data. It does not change any validation results, but it makes some schemas invalid that would be otherwise valid according to JSON Schema . var str = callsite.getFunctionName() Inherited from V8 older versions of JavaScript. How to flip an image on hover using CSS ? As an example, in normal JavaScript, mistyping a variable name creates a new (Using eval keeps the context at the point of invocation.). Rule #1: How JavaScript Implicit Binding Works. The "use strict" directive was new in ECMAScript version 5. How to get file input by selected file name without path using jQuery ? It applies to both function and nested functions. How to combine several legends in one frame? There are two ways to use it: In global scope: Use Strict Mode for the entire script. Strict mode is declared by adding "use strict"; to the beginning of a What was the actual cockpit layout and crew of the Mi-24A? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. arguments objects for strict mode functions store the original arguments when the function was invoked. if you are using an object literal for your methods and no actual method name, then this will not work as arguments.callee acts like an anonymous function which will not carry any function name. Strict mode has been designed so that the transition to it can be made gradually. Thanks for contributing an answer to Stack Overflow! In strict mode, it is now undefined. The problem with with is that any name inside the block might map either to a property of the object passed to it, or to a variable in surrounding (or even global) scope, at runtime; it's impossible to know which beforehand. This syntax has a flow, it isnt possible to blindly concatenate non-conflicting scripts. How to execute a JavaScript function when I have its name as a string. "use strict"; Defines that How to pop an alert message box using PHP ? Also, to get only the name of the function, you need to use arguments.callee.name. Find centralized, trusted content and collaborate around the technologies you use most. Benefits of using use strict: Strict mode makes several changes to normal JavaScript semantics. Declared at the beginning of a script, it has global scope (all code To subscribe to this RSS feed, copy and paste this URL into your RSS reader. (Use call, apply, or bind to specify a particular this.) assignment to a non-writable data property, assignment to a getter-only accessor property, Declaring two function parameters with the same name, Declaring the same property name twice in an object literal, Assigning to an undeclared variable throws a, Failing to assign to an object's property (e.g. Many compiler optimizations rely on the ability to say that variable X is stored in that location: this is critical to fully optimizing JavaScript code. Strict mode throws in such cases. See. are on the stack, but it will include the value of each argument that ES6 class methods. You can enable strict mode in two different ways, globally and locally. Until ES2015, there was no standard way to get the name of a function. Only concatenating strict and non-strict scripts is problematic. What was the purpose of laying hands on the seven in Acts 6:6. The execution context is not the global object anymore, contrary to above case 2.1. You cannot deprecate/obsolete/kill that which is actively used all over the web. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. In strict mode, the arguments object is created and initialized with the same values than the named arguments, but changes to either the arguments object or the named arguments aren't reflected in one another. of it. How to check whether a string contains a substring in JavaScript? In ES5 and above, there is no access to that information. Still, this hiding makes little sense and is probably undesirable (it might hide a typo, for example), so in strict mode, duplicate argument names are a syntax error: Strict mode forbids a 0-prefixed octal literal or octal escape sequence. The only option this leaves you if you need to support IE is trying to parse the name from the function's string representation, which is not a good idea. @ChrisDutrow: Depends on your requirements. Note: In function calls like f(), this value was the global object. Looks nice. It helps you to write cleaner code, Share Improve this answer Follow answered Feb 19, 2015 at 11:58 Vlad A. Ionescu 2,578 1 16 19

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