Why isn't my JavaScript working in JSFiddle?

javascript

event-listeners

function-declaration

scope-and-closures

byAlex Kataev·Aug 28, 2024

For your JavaScript to perform smoothly in JSFiddle, use these steps:

Opt for No wrap - in <body> or No wrap - in <head>, to dodge load type issues.
Match the framework/library version to your code’s specific needs in the settings.
Include all external resources correctly.
Ensure there are no syntax errors.

Try this simple config shift:

// In your fiddle settings:
// Select: No wrap - in <body>

Consider these pointers to debug your JS in JSFiddle.

Configuration: Wrapping options explained

By default, JSFiddle sets JavaScript wrapping to onLoad which limits your functions' access to a local scope only. To have your functions broadly accessible, simply change the wrapping to:

No wrap - in <head>: Runs your code synchronously.
No wrap - in <body>: Runs your code after the entire page has loaded.

// Hold my beer
// Select: No wrap - in <body>

The utility of function declaration and the window object

Declare your functions directly on the window object for global access across your script. Alternatively, you can avoid wrapping your functions using var.

window.myEpicFunction = function() { /* ... */ };
// or
function myEpicSolution() { /* ... */ }

Unobtrusive JavaScript: Event listeners vs inline event handlers

Save yourself some headache by using event listeners in your JavaScript instead of inline event handlers. Putting all event listeners into your JavaScript ensures a smooth script execution.

// Let there be click!
document.getElementById('myButton').addEventListener('click', myEpicFunction);

Framework selection in JSFiddle

Using No Library (pure JS) in the framework selection of JSFiddle simplifies the debugging process when you are not using any JavaScript library. Additionally, it prevents potential conflicts.

Designing and debugging your code

Invest time in keeping your JavaScript concise and organized. This not only saves you debugging time but also helps others who may need to understand your code.

Diving deeper

Handling events with jQuery

jQuery simplifies event handling. Once you have selected it as your framework of choice in JSFiddle, confirm that its version matches with that of your code.

// Ring ring, document ready!
$(document).ready(function() { /* Your code here */ });

Wrangling scope and closures

Dealing with scope and closures can be tricky. Always be mindful of function scopes within loops and callbacks to avoid unexpected errors.

// Round and round we go
for (var i = 0; i < 5; i++) {
  (function(i) {
    // Your code with the current i
  })(i);
}

Ensuring element availability

Always confirm an element's availability in the DOM before trying to interact with it.

// Ready or not, here I come!
document.addEventListener('DOMContentLoaded', function () { /* Initialization code */ });

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