How To Handle Reference Error In Javascript
Contents |
& Guides Learn the Web Tutorials References Developer Guides Accessibility Game development ...more docs Mozilla Docs Add-ons Firefox WebExtensions Developer ToolsFeedback
Reference Error Is Not Defined Javascript
Get Firefox help Get web development help Join the MDN community referenceerror: function is not defined Report a content problem Report a bug Search Search Languages Deutsch (de) Français (fr) 日本語 (ja) 한국어 referenceerror javascript (ko) 中文 (简体) (zh-CN) Add a translation Edit Advanced Advanced History Print this article MDN Web technology For developers JavaScript JavaScript reference JavaScript error reference ReferenceError: "x" is not
Referenceerror Variable Is Not Defined
defined Your Search Results fscholz ReferenceError: "x" is not defined In This Article MessageError typeWhat went wrong?ExamplesVariable not declaredWrong scopeSee also Message ReferenceError: "x" is not defined Error type ReferenceError. What went wrong? There is a non-existent variable referenced somewhere. This variable needs to be declared, or you need make sure it is available in your current script or
Referenceerror $ Is Not Defined Jquery
scope. Note: When loading a library (such as jQuery), make sure it is loaded before you access library variables, such as "$". Put the script tag that loads the library before your code that uses it. Examples Variable not declared foo.substring(1); // ReferenceError: foo is not defined The "foo" variable isn't defined anywhere. It needs to be some string, so that the String.prototype.substring() method will work. var foo = "bar"; foo.substring(1); // "ar" Wrong scope A variable need to be available in the current context of execution. Variables defined inside a function cannot be accessed from anywhere outside the function, because the variable is defined only in the scope of the function function numbers () { var num1 = 2, num2 = 3; return num1 + num2; } console.log(num1); // ReferenceError num1 is not defined. However, a function can access all variables and functions defined inside the scope in which it is defined. In other words, a function defined in the global scope can access all variables defined in the global scope. var num
here for a quick overview of the site Help Center Detailed answers to any questions you might have Meta Discuss the workings and policies of this site About Us Learn more javascript exception object about Stack Overflow the company Business Learn more about hiring developers or posting
Javascript Error Handling Best Practices
ads with us Stack Overflow Questions Jobs Documentation Tags Users Badges Ask Question x Dismiss Join the Stack Overflow Community Stack referenceerror is not defined node js Overflow is a community of 4.7 million programmers, just like you, helping each other. Join them; it only takes a minute: Sign up How to handle 'undefined' in javascript [duplicate] up vote 21 down https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Errors/Not_defined vote favorite 4 Possible Duplicate: Detecting an undefined object property in JavaScript From the below javascript sample try { if(jsVar) { proceed(); } }catch(e){ alert(e); } this jsVar is declared and initialed in another js fine. The problem is that code throws undefined error when this code is executed before the other file (where its declared and initiated) is executed. That is why it is surrounded by try and http://stackoverflow.com/questions/1984721/how-to-handle-undefined-in-javascript catch. Whats the best way to handle this undefined error than try catch? javascript share|improve this question asked Dec 31 '09 at 9:49 Madhu 2,63772346 marked as duplicate by casperOne Jan 12 '12 at 16:35 This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question. add a comment| 3 Answers 3 active oldest votes up vote 47 down vote accepted You can check the fact with if (typeof(jsVar) == 'undefined') { ... } share|improve this answer answered Dec 31 '09 at 9:50 alex.zherdev 16.4k64453 Does this have any advantage over "my" way? –Jan Hančič Dec 31 '09 at 9:54 It may throw an error: jsVar is not defined. You should test it this way : if (window.jsVar !== undefined) {}. It seems like typeof() "catches" this error. –Fabien Ménager Dec 31 '09 at 10:15 @Fabien: Or perhaps use if("jsVar" in window){}... but I would avoid code that would require coding for this error case. –Thomas Eding Jan 1 '10 at 9:51 Should this be === ? –logic-unit Apr 30 '14 at 10:58 @logic-unit that is in theory better, but
Learn Bootstrap Learn Graphics Learn Icons Learn How To JavaScript Learn JavaScript Learn jQuery Learn jQueryMobile Learn AppML Learn AngularJS Learn JSON Learn AJAX Server Side Learn SQL Learn PHP Learn ASP Web Building Web Templates Web Statistics Web Certificates XML Learn XML http://www.w3schools.com/js/js_errors.asp Learn XML AJAX Learn XML DOM Learn XML DTD Learn XML Schema Learn XSLT Learn XPath Learn XQuery × HTML HTML Tag Reference HTML Event Reference HTML Color Reference HTML Attribute Reference HTML Canvas Reference HTML SVG Reference Google https://tommcfarlin.com/javascript-reference-error-is-not-defined/ Maps Reference CSS CSS Reference CSS Selector Reference W3.CSS Reference Bootstrap Reference Icon Reference JavaScript JavaScript Reference HTML DOM Reference jQuery Reference jQuery Mobile Reference AngularJS Reference XML XML Reference XML Http Reference XSLT Reference XML Schema Reference is not Charsets HTML Character Sets HTML ASCII HTML ANSI HTML Windows-1252 HTML ISO-8859-1 HTML Symbols HTML UTF-8 Server Side PHP Reference SQL Reference ASP Reference × HTML/CSS HTML Examples CSS Examples W3.CSS Examples Bootstrap Examples JavaScript JavaScript Examples HTML DOM Examples jQuery Examples jQuery Mobile Examples AngularJS Examples AJAX Examples XML XML Examples XSLT Examples XPath Examples XML Schema Examples SVG Examples Server Side PHP Examples ASP Examples Quizzes HTML Quiz CSS Quiz JavaScript Quiz Bootstrap Quiz jQuery is not defined Quiz PHP Quiz SQL Quiz XML Quiz × JS Tutorial JS HOME JS Introduction JS Where To JS Output JS Syntax JS Statements JS Comments JS Variables JS Operators JS Arithmetic JS Assignment JS Data Types JS Functions JS Objects JS Scope JS Events JS Strings JS String Methods JS Numbers JS Number Methods JS Math JS Random JS Dates JS Date Formats JS Date Methods JS Arrays JS Array Methods JS Array Sort JS Booleans JS Comparisons JS Conditions JS Switch JS Loop For JS Loop While JS Break JS Type Conversion JS RegExp JS Errors JS Debugging JS Hoisting JS Strict Mode JS Style Guide JS Best Practices JS Mistakes JS Performance JS Reserved Words JS JSON JS Forms JS Forms Forms API JS Objects Object Definitions Object Properties Object Methods Object Prototypes JS Functions Function Definitions Function Parameters Function Invocation Function Closures JS HTML DOM DOM Intro DOM Methods DOM Document DOM Elements DOM HTML DOM CSS DOM Animations DOM Events DOM EventListener DOM Navigation DOM Nodes DOM Nodelist JS Browser BOM JS Window JS Screen JS Location JS History JS Navigator JS Popup Alert JS Timing JS Cookies JS JSON JSON Intro JSON Syntax JSON HowTo JSON Http JSON Files JSON SQL JS Examples JS Examples JS HTML DOM JS HTML Input JS HTML Objects JS HTML Events JS Browser JS Quiz JS Certificate JS
/ 5 CommentsTwo Solutions for "JavaScript Reference Error Is Not Defined"If you're working on any type of web site or web application that has any other dependencies either for its front-end framework - such as Bootstrap and Foundation - or from the site's foundation - such as Rails or WordPress - there's a chance that your own JavaScript sources may result in the following:Reference Error [variable] is not defined.In some cases, this can be simply referring to a variable that isn't defined (perhaps the most popular is when jQuery's $ function has been dereferenced and you're trying to use $) and simply needs a definition.But, in other cases, there are times where it may not be as simple."JavaScript Reference Error is Not Defined"As mentioned, there are times in which simply defining a variable will resolve the issue. For example, given the example with jQuery above, we can make a call to noConflict() to restore the variable.Old references of $ are saved during jQuery initialization; noConflict() simply restores them.But that's getting beyond the point of this article.The thing is, simply restoring a variable or giving it a definition especially when it's related to a third-party dependency is not as easy.Instead, the problem can usually be resolved in one of two ways.1. Load the Libraries in Proper OrderArguably, the most popular reason for seeing a ReferenceError has to do with the fact that our script is referencing a variable that has yet to be defined.To fix this, it's generally a problem of the files being loaded out of order and this is especially true if the error is being thrown in the context of a site or web application that has its own libraries, then the scripts are probably loading later than your own.This means that either the scripts are placed after yours in the head element of the page or they are being loaded in the footer of the page. If that's the case, most frameworks and applications provide an API for setting the order in which files are loaded, setting dependencies, and then defining where, in the page, they are loaded.2. Leverage Undefined ValuesAnother more slightly involved example involves calling a function with an optional parameter and then checking to see if that argument is defined when the function is called.For example, let's say that we know that the function in question will be called at two points within the page lifecycle:When the DOM is ready, and l