Why are my JavaScript functions not defined in JSFiddle?

Why JavaScript isn't Running on JSFiddle: Resolving Function Definition Errors

When attempting to run JavaScript code on JSFiddle, you may encounter errors indicating that specific functions are not defined. This occurs because JSFiddle encapsulates code within an onload function, limiting the scope of function definitions.

Function Definition and Referencing

In the provided code, functions such as fillList() and mySelectList() are defined within the window.onload function. This means that these functions are only accessible from within this function. However, you are trying to reference them as global variables in your HTML, leading to the errors.

Resolution Options

To resolve this, you have three options:

a) Modifying Functions as Global Variables

• The simplest and quickest, but not ideal, solution is to change the function definition syntax to:

<code class="javascript">window.fillList = function() {}; // makes fillList a global function</code>

b) Unobtrusive JavaScript

• The recommended approach is to utilize unobtrusive JavaScript, which separates HTML from JavaScript:

<code class="javascript">// attach event listener from within JavaScript
var mySelectList = document.getElementById('mySelectList');
mySelectList.addEventListener('change', function() {
    alert('Selection changed!');
});</code>

c) Modifying JSFiddle Settings

• JSFiddle allows you to specify wrapping options. Change the encapsulation setting to "No wrap - Head or Body" to prevent code containment within an onload function.

Recommendation

Option b) is highly recommended as it promotes best practices and code organization. By separating HTML from JavaScript, you gain greater control and flexibility over your code.

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