Why do strings sometimes get changed to numbers in javascript?

I have this code:

function getSessionGUID() {
   return (S4()+S4());
}

function S4() {
   return (((1+Math.random())*0x10000)|0).toString(16).substring(1);
}

It clearly returns a string, but if you run it a bunch of times, you can notice that it sometimes returns infinity.

for (var i = 0; i < 100000; i++){ if(getSessionGUID() == Infinity) console.log(\"INFINITY\"); }
871 x INFINITY

I then noticed that if you remove the |0, it solves the problem:

function S4() {
   return (((1+Math.random())*0x10000)|0).toString(16).substring(1);
}

Results:

for (var i = 0; i < 100000; i++){ if(getSessionGUID() == Infinity) console.log(\"INFINITY\"); }
undefined

Why does this happen? In both cases the value is changed into a string.

Rating: 1 out of 5 based on 5 ratings

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