javascript get current function name in strict mode

I already mentioned it. When a function is called in non-strict mode, this refers to the global object which is a window in the browser and global on Node.js. 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. When adding 'use strict';, the following cases will throw a SyntaxError before the script is executing: These errors are good, because they reveal plain errors or bad practices. In my case, it had to do with mocking and spying during tests. 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. Non-standard: This feature is non-standard and is not on a standards track. The property of ampere const object can be changed but e cannot shall changed to ampere reference on to recent object How to call PHP function on the click of a Button ? google apps script: get the name of the function that is currently running. 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. Also, this technique cannot work with anonymous functions. Strict mode throws in such cases. You could convert your function into a string (fn + '') and split it later at whitespace and open bracket /\s|\(/. Strict mode forbids setting properties on primitive values. The guides area is designed to help developers learn to better interact with the date and time problem domain, and the Moment.js library. This is the same answer you got before, just wrapped up in a nice module, and using some V8-specific APIs. JavaScript : Can I get the name of the currently running function in JavaScript? Strict mode removes most cases where this happens, so the compiler can better optimize strict mode code. I've moved code around and forgotten to update the hard-coded function names. inspect them further. Or will it be in future plans ECMA6, 7? Strict mode prohibits some syntax likely to be defined in future versions of ECMAScript. This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. Given a function and the task is to get the name of function that is currently running using JavaScript. If it's dynamic, you're already accessing it by name, or no? 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. Get the wrapping function name in Javascript, get invoked method name and passed in parameters. All what you need is simple. How? How to execute a JavaScript function when I have its name as a string. Why? How do I include a JavaScript file in another JavaScript file? MyFunction doesn't call the handler so querying arguments. // So codes below the line 'use strict' will be executed in strict mode. operator, SyntaxError: redeclaration of formal parameter "x". Enable strict mode globally by adding the string "use strict" as the first statement in your file. @ChrisDutrow: Depends on your requirements. It doesn't apply to block statements enclosed in {} braces; attempting to apply it to such contexts does nothing. Btw, I am using VisualStudio Code and havent look at automatic refactoring tools for JavaScript. Creating Error object for each calling is just a hack, not a working method. The guides section is new and still under construction. 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. This is also why things like the name attribute on form fields or expressions like 'form.myField.value' still work. JSLint is suddenly reporting: Use the function form of "use strict". Although that assumes that no value with the same name will collide (a reasonable assumption in many cases, and not so reasonable in others). Is there any plans to make module standard for nodejs? @Firanolfind I have no idea what you mean. 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. How to get function name in strict mode [proper way], stackoverflow.com/questions/618820/logging-vs-debugging/. If (like me) you want to define this elsewhere and call it generically, you can store the code as a string somewhere global or import it, then eval() it wherever to access the current function name. How to get the function name from within that function using JavaScript ? Looking for job perks? Once enabled, the strict mode affects the execution context, making this to be undefined in a regular function invocation. Assignments which would accidentally create global variables throw an error in strict mode: Strict mode makes assignments which would otherwise silently fail to throw an exception. Great job. As an example, in normal JavaScript, mistyping a variable name creates a new exebook For logging/debugging purposes, you can create a new Error object in the logger and inspect its .stack property, e.g. It is possible to change each file individually and even to transition code to strict mode down to the function granularity. property, a non-existing property, a non-existing variable, or a non-existing It applies to both function and nested functions. How to get the function name under "use strict"? Thorough testing will need to be performed to make sure nothing breaks. How a top-ranked engineering school reimagined CS curriculum (Ep. For logging/debugging purposes, you can create a new Error object in the logger and inspect its .stack property, e.g. How to get variable name in annonymous function construnction var f = function(){}; How do I remove a property from a JavaScript object? However, inspection revealed that this worked: @TomAnderson with your change, you're now getting the name of. How to find inputs with an attribute name starting with specific letter or text using jQuery? Find centralized, trusted content and collaborate around the technologies you use most. Accessing a property on a primitive implicitly creates a wrapper object that's unobservable, so in sloppy mode, setting properties is ignored (no-op). Was Stephen Hawking's explanation of Hawking Radiation in "A Brief History of Time" not entirely accurate? Oh that's why people always beat me on the speed to reply. This is why W3C's attempts to deprecate tags like and has failed. throw myFunctionName() + ': invalid number of arguments'; For now I have to hard-code the function name within the throws. Note: Using Function.caller is non-standard and arguments.callee is forbidden in strict mode. How about saving the world? rev2023.4.21.43403. If total energies differ across different software, how do I decide which software to use? JavaScript sometimes makes this basic mapping of name to variable definition in the code impossible to perform until runtime. It includes code to get the name of functions, which works in most browsers. Why did US v. Assange skip the court of appeal? You can click the functions or objects to Some websites now provide ways for users to write JavaScript which will be run by the website on behalf of other users. Find centralized, trusted content and collaborate around the technologies you use most. , so the answer from @Sayem is only valid if you aren't using strict mode. // Strict mode syntax for entire script. Logging and debugging have different use and often logging is more productive over the time (. ES6 class methods. To enable strict mode for your javascript code, all you have to do is add the string "use strict" at the beginning of the code. Fortunately, this careful review can be done gradually down the function granularity. *only with JSON Schema ** only with JSON Type Definition # Strict mode options v7 # strict By default Ajv executes in strict mode, that is designed to prevent any unexpected behaviours or silently ignored mistakes in schemas (see Strict Mode for more details). How to change an HTML element name using jQuery ? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. These differences are very subtle differences. (Using eval keeps the context at the point of invocation.). 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. If you want to get name from outside you may parse it out of: but I think name property of function object might be what you need: this however does not seem work for IE and Opera so you are left with parsing it out manually in those browsers. SyntaxError: Unexpected '#' used outside of class body, SyntaxError: unlabeled break must be inside loop or switch, SyntaxError: unparenthesized unary expression can't appear on the left-hand side of '**', SyntaxError: Using //@ to indicate sourceURL pragmas is deprecated. How to get the class of a element which has fired an event using JavaScript/JQuery? rev2023.4.21.43403. Example: strict mode. Introductory Concepts. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. If I want to add console.debug(current function name)inside 10 functions , to put actual name within each function is annoying and error prone. How to check whether a string contains a substring in JavaScript? Has depleted uranium been considered for radiation shielding in crewed spacecraft beyond LEO? Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Examples might be simplified to improve reading and learning. Then the answer is there is none, which is why I asked for clarification. All browser compatibility updates at a glance, Frequently asked questions about MDN Plus. The "use strict" directive can only be applied to the body of functions with simple parameters. Not using eval if you don't really need it may be another pragmatic solution. arguments.callee unfortunatelly deprecated, and using it throws an error in "strict mode". In strict mode, a variable can not be used before it is declared: In strict mode, eval() can not declare a variable using the var keyword: eval() can not declare a variable using the let keyword: The this keyword in functions behaves Visit Mozilla Corporations not-for-profit parent, the Mozilla Foundation.Portions of this content are 19982023 by individual mozilla.org contributors. Rule #1: How JavaScript Implicit Binding Works. What is the difference between call and apply? Though, in some implementations you can simply get the name using arguments.callee.name. This is a good part of the language being strict about throwing errors: it leaves room for future semantic changes. 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. If history has proven anything, then it's the opposite: What works today is about the only thing guaranteed to work in tomorrow's browsers as well. Strict mode has been designed so that the transition to it can be made gradually. If your code base contains such cases, testing will be necessary to be sure nothing is broken. In older versions of JS you can get it by using arguments.callee.. You may have to parse out the name though, as it will probably include some extra junk. The "use strict" directive was new in ECMAScript version 5. Just call console.trace() and Firebug will write a very informative For example, Chrome defines it as an own data property, while Firefox and Safari extend the initial poison-pill Function.prototype.caller accessor to specially handle this values that are non-strict functions. Strict mode makes several changes to normal JavaScript semantics: Eliminates some JavaScript silent errors by changing them to throw errors. If you use Node.js there is a useful package exactly for this problem: caller-id. variable and dies. You can only get the name of a function you have a reference to, and you cannot get a reference to an arbitrary function in the call stack. Attempts to delete a non-configurable or otherwise undeletable (e.g. For those frames, getFunction() will return undefined. See ; non-standard and not allowed in strict mode, developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/. Reconstructing the stack and recursion Note that in case of recursion, you can't reconstruct the call stack using this property. Not the answer you're looking for? it's read-only) throws a, Deleting a non-deletable property throws a. A-143, 9th Floor, Sovereign Corporate Tower, We use cookies to ensure you have the best browsing experience on our website. How to get file input by selected file name without path using jQuery ? In implicit binding, you need to check the object adjacent to the method at the invocation time. For this, just out exact statement "use strict"; at the start of the script that is before any other statements. How to get JS class name from class, but not from instance? How do I get the current date in JavaScript? 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. Here we make use of an assignment operator and variable to stow the function as an object, then utilizing that variable, we will be capable to invoke the . "use strict" is just a string, so IE 9 will not throw an error even if it does not understand it. A minor scale definition: am I missing something? Recent answer is no more than dirty hack and not acceptable for me answer. How to get the function name from within that function? of it. Beginner kit improvement advice - which lens should I consider? Strict mode changes both syntax and runtime behavior. Which was the first Sci-Fi story to predict obnoxious "robo calls"? In strict mode, a function declaration inside a block is only visible inside the block. Both extensions are problematic for "secure" JavaScript because they allow "secured" code to access "privileged" functions and their (potentially unsecured) arguments. For example: Octal escape sequences, such as "\45", which is equal to "%", can be used to represent characters by extended-ASCII character code numbers in octal. All subsequent code in the script will execute in strict mode. Doing this is usually a hacky solution to a deeper underlying problem. It can be applied to individual functions. Can you recommend some? In strict mode, any assignment to a non-writable property, a getter-only In sloppy mode, eval("var x;") introduces a variable x into the surrounding function or the global scope. 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. You can bind function as its context then you can access its name via this.nameproperty: After little research here is a good solution : Source : https://gist.github.com/dfkaye/6384439, Building on @georg solution, this one returns just the function name. Is there a generic term for these trajectories? Is there a weapon that has the heavy property and the finesse property (or could this be obtained)? Moreover . For strict, arrow, async, and generator functions, accessing the caller property throws a TypeError. 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. Confirmed working in Node v16.13.0. The getMyName function in the snippet below returns the name of the calling function. This page was last modified on Apr 12, 2023 by MDN contributors. Print the content of a div element using JavaScript, JQuery | Set the value of an input text field. Not only is automatic boxing a performance cost, but exposing the global object in browsers is a security hazard because the global object provides access to functionality that "secure" JavaScript environments must restrict. W3Schools is optimized for learning and training. Making statements based on opinion; back them up with references or personal experience. We use cookies to personalise content and ads, to provide social media features and to analyse our traffic. Difference between var and let in JavaScript, Convert a string to an integer in JavaScript. was passed to each function. @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. To learn more, see our tips on writing great answers. var str = callsite.getFunctionName() Inherited from V8 differently in strict mode. Why is it shorter than a normal address? Can I get the name of the currently running function in JavaScript? What differentiates living as mere roommates from living in a marriage-like relationship? It's surprising nobody else has pointed that out in the almost 3 years this answer has been here :-). To subscribe to this RSS feed, copy and paste this URL into your RSS reader. 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. Source: Javascript - get current function name. BCD tables only load in the browser with JavaScript enabled. What was the actual cockpit layout and crew of the Mi-24A? I would like to have a rudimentary debugging function like this (with npmlog defining log.debug ): 6 1 function debug() { 2 var callee, line; 3 /* MAGIC */ 4 log.debug(callee + ":" + line, arguments) 5 } 6 When called from another function it would be something like this: In sloppy mode, modifying a value in the arguments object modifies the corresponding named argument. As noted this applies only if your script uses "strict mode". of JavaScript. However, arguments.callee.name is only available from inside the function. Get the size of the screen, current web page and browser window. StackExchange.ready(function(){$.get("https://stackoverflow.com/posts/38435450/ivc/7a17");}); Read More how to monitor the network on node.js similar to chrome/firefox developer tools?Continue, Read More Call AngularJS from legacy codeContinue, Read More How can I add multiple sources to an HTML5 audio tag, programmatically?Continue, Read More webpack: Module not found: Error: Cant resolve (with relative path)Continue, Read More Why doesnt a Javascript return statement work when the return value is on a new line?Continue, Read More How to set time with date in momentjsContinue, The answers/resolutions are collected from stackoverflow, are licensed under. Can you still use Commanders Strike if the only attack available to forego is an attack against an ally? Changes generally fall into these categories: Strict mode changes some previously-accepted mistakes into errors. How to get the ID of the clicked button using JavaScript/jQuery ? Is there any new proper(standard) alternative for getting function name inside actual function? Strict mode can be enabled using some directives such as 'use strict'. We address our most frequently seen support requests here, so it is a great place to check for solutions to any issues you may have. In strict mode, assigning to NaN throws an exception. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Table Of Contents duplicating parameter in regular JS function; duplicating parameter in non strict mode; duplicating parameter in strict mode; How do arrow functions treat duplicate parameters The arguments inside the error function refers to this method's own arguments object. The entire concatenation looks strict, the inverse is also true. In strict mode you can no longer reference callee (see the related discussion at Javascript: is the arguments array deprecated?) 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