How to test JavaScript code performance

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<script src="http://http://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script> 
 <script>
console.time('timerName');
    $(document).ready(function(e) {
        alert(); // Your javascript code to test here

    });
console.timeEnd('timerName');
</script>


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