Math.random() javascript function undefined on Chrome

Question

In first place, I am convinced that this is a trivial question, but I cannot understand why this is happening and I couldn't find an answer anywhere else. I googled my issue with little success, but if I missed something and just wasted your time please point me in the right direction and accept my humble excuses.

That said, here is what happens. I am building a simple script to display a graph drawn by a distributed algorithm (giraph) and I am working on Linux. I import all the libraries and, in particular, jQuery and everything works in Firefox (version 36.0.1). Switching to Chrome (version 41.0.2272.89 (64-bit)), the page stops working. Investigating the issue, I found out that the error was inside the jQuery.extend() function into the jQuery library, at the following line:

expando: "jQuery" + ( version + Math.random() ).replace( /\D/g, "" ),

In fact, trying to invoke Math.random() into the browser console leads to:

> Math.random();
> Uncaught TypeError: Undefined is not a function

Anyway, while typing the console autocompletes the "Math" variable, with the following result:

> Math
> function (){return "";}

This does not happen with Chrome on MacOS X Mavericks. Did anybody experience this kind of behaviour before?

EDIT: Unfortunately, I don't think that this is a namespace conflict. In my library I import only one other library (other than jQuery), which is Sigma js. As suggested, I wrote Math in the console and tried to understand which library did override Math (using "Show Function Definition"), with the following result, taken from a file named "VM53" (which I did not write and/or linked directly).

(function (){
    for (var i in window)
    {
    try {
            var jsType = typeof window[i];
            switch (jsType.toUpperCase())
            {                   
                case "FUNCTION": 
                    if (window[i] !== window.location)
                    {
                        if (window[i] === window.open || (window.showModelessDialog && window[i] === window.showModelessDialog))
                            window[i] = function(){return true;};
                        else if (window[i] === window.onbeforeunload)   // To try to fix onbeforeunload pop ups some users report seeing but I can't replicate.
                            window.onbeforeunload = null;
                        else if (window[i] === window.onunload)
                            window.onunload = null;                             
                        else
                            window[i] = function(){return "";};
                    }
                    break;                          
            }           
        }
        catch(err)
        {}      
    }

    for (var i in document)
    {
        try {
            var jsType = typeof document[i];
            switch (jsType.toUpperCase())
            {                   
                case "FUNCTION":
                    document[i] = function(){return "";};
                    break;                  
            }           
        }
        catch(err)
        {}      
    }

    try {
        eval = function(){return "";};              
        unescape = function(){return "";};
        String = function(){return "";};
        parseInt = function(){return "";};
        parseFloat = function(){return "";};
        Number = function(){return "";};
        isNaN = function(){return "";};
        isFinite = function(){return "";};
        escape = function(){return "";};
        encodeURIComponent = function(){return "";};
        encodeURI = function(){return "";};
        decodeURIComponent = function(){return "";};
        decodeURI = function(){return "";};
        Array = function(){return "";};
        Boolean = function(){return "";};
        Date = function(){return "";};
        Math = function(){return "";};
        Number = function(){return "";};
        RegExp = function(){return "";};

        var oNav = navigator;
        navigator = function(){return "";};
        oNav = null;            
    }
    catch(err)
    {}

})();

Some script overrided Math.random. Try to remove other <script> tags from page and see what causes error. — Ginden
– Ginden, Commented Mar 16, 2015 at 8:55
Or a Chrome extension disables Math for some reason. Does it work if you try it in incognito mode? — JJJ
– JJJ, Commented Mar 16, 2015 at 8:57
Math.random() is native JavaScript code, so the only thing that comes to my mind is that somewhere in your code you have overwritten Math object. — Roumelis George
– Roumelis George, Commented Mar 16, 2015 at 8:59

Boris Zagoruiko · Accepted Answer · 2016-11-16 00:51:20Z

11

Something overrides Math in your code.

Execute Math in your chrome console. Execute context menu on it and select "Show function definition". This will probably lead you to "Sources" panel and show script where it is being overriden.

EDIT: this is chrome extension called notscripts. Disable it. Here is the source code for proof: webarchive

edited Nov 16, 2016 at 0:51

answered Mar 16, 2015 at 9:04

Boris Zagoruiko

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4 Comments

Boris Zagoruiko Over a year ago

if everything is fine and you found this stuff, find its author on GitHub, build trust with him, get his home address, find something very heavy and show this a*****e that overriding language is the bad idea indeed =)

Alessio Arleo Over a year ago

As I said, I knew it was something trivial grabs cone of shame.

Alexis Wilke Over a year ago

Glen, the link is now broken. I would suggest pointing it here now: code.google.com/archive/p/notscripts

Boris Zagoruiko Over a year ago

@AlexisWilke Thanks for pointing it out. I replace link with webarchive cached copy.

jasonscript · Accepted Answer · 2015-03-16 08:59:56Z

2

Another library on your page is overriding the Math object. This is one of the reasons that polluting the Global Namespace is frowned upon.

For reference Math should return the following

enter image description here

answered Mar 16, 2015 at 8:59

jasonscript

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Comments

Mark · Accepted Answer · 2016-05-04 21:17:07Z

1

I found another situation that could cause this to happen. I was converting a PHP function to a JS function and I had the following line:

ticks += "," . Math.floor(yyy * intMax);

Changing it to

ticks += "," + Math.floor(yyy * intMax);

solved the problem

answered May 4, 2016 at 21:17

Mark

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1 Comment

Alexis Wilke Over a year ago

That really had nothing to do with the problem. Math.random() is clearly a JavaScript function and it should continue to work for pretty much ever.

Alexis Wilke · Accepted Answer · 2016-11-15 20:46:11Z

0

Somehow, NotScript got automatically installed in my Chrome browser on Ubuntu 16.04. That inserts the script you show in your update just after the <html> tag.

I had to go to the settings, look at the extensions, disable the NotScripts and then restart Chrome to it would be gone.

On Ubuntu, this must be very recent or the script got updated recently because I ran the exact same test in Chrome, with the exact same scripts, a few days ago, and it was working just fine.

Interestingly enough, it looks like it was removed 2 years ago (Nov 2014) and maybe re-added recently?

answered Nov 15, 2016 at 20:46

Alexis Wilke

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