if function does not exist write function - javascript

javascript function typeof
Bret Thomas picture Bret Thomas · Jan 12, 2012 · Viewed 13.3k times · Source

In php I'm writing the following

<?php
if(x != 0) {
echo "function myfunction(){};";    
}
?>

In javascript I wish to test if the function exists and if not write out an empty function

if(typeof myfunction != 'function'){
    function myfunction(){};
}

This works great in firefox but, in chrome even if the typeof equals function it still goes into and creates the empty function. I can't find a work around for chrome, i've tried if(!myfunction), if(typeof window.myfunction != 'function) but nothing seems to work here for chrome when everything seems to work in firefox. Any ideas?

Answer

Quentin picture Quentin · Jan 12, 2012

Use a function expression, not a function declaration.

if(typeof myfunction != 'function'){
   window.myfunction = function(){};
}

(I'm using window since your last paragraph suggests you want a global function)

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