Why isn't my JavaScript working in JSFiddle?

If you do not specify the wrap setting it defaults to "onLoad". This results with all JavaScript being wrapped in a function run after result has been loaded. All variables are local to this function thus unavailable in the global scope.

Change the wrapping setting to "no wrap" and it'll work:

http://jsfiddle.net/zalun/Yazpj/1/

I switched the framework to "No Library" as you don't use any.

The function is being defined inside a load handler and thus is in a different scope. As @ellisbben notes in the comments, you can fix this by explicitly defining it on the window object. Better, yet, change it to apply the handler to the object unobtrusively: http://jsfiddle.net/pUeue/

$('input[type=button]').click( function() {
   alert("test");   
});

Note applying the handler this way, instead of inline, keeps your HTML clean. I'm using jQuery, but you could do it with or without a framework or using a different framework, if you like.

There is another way, declare your function into a variable like this :

test = function() {
  alert("test");
}

jsFiddle

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Details

EDIT (based on the comments of @nnnnnn)

@nnnnnn :

why saying test = (without var) would fix it ?

When you define a function like this :

var test = function(){};

The function is defined locally, but when you define your function without var :

test = function(){};

test is defined on the window object which is at the top level scope.

why does this work?

Like @zalun say :

If you do not specify the wrap setting it defaults to "onLoad". This results with all JavaScript being wrapped in a function run after result has been loaded. All variables are local to this function thus unavailable in the global scope.

But if you use this syntax :

test = function(){};

You have an access to the function test because it's defined globally

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References :

• https://stackoverflow.com/a/338053/3083093
• https://stackoverflow.com/a/5830423/3083093