What does this random return

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Hello,

I am trying to understand what the random function does in this function. here is the original purpose of this function

This function returns an array that contains a scrambled list of values. There are exactly four pairs of numbers (1,2,3 and 4) and one unpaired number (5) in the array. The values in the array are scrambled by using the array.sort() method to sort the array in a pseudo random way.

JavaScript

function randomAnswers(){
    var answers = [1,1,2,2,3,3,4,4,5];
    answers.sort(function(item){
        return .5 - Math.random();
    })
    return answers;
}

What I have tried:

I know that random returns numbers between 0(included) to 1(not included). but I dont get .5 -Math.random(); in this function

Posted 27-Nov-17 12:34pm

mappleleaf

Updated 27-Nov-17 14:44pm

PIEBALDconsult

v3

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Dave Kreskowiak · Answer 1 · 2017-11-27T13:23:00

Solution 1

What's not to understand?

It's just math. Generate a random number between 0 and 1 (inclusive), subtract that from 0.5 and return the result to whatever code called this code.

Posted 27-Nov-17 13:23pm

Dave Kreskowiak

PIEBALDconsult · Answer 2 · 2017-11-27T14:44:00

Solution 2

If it works like .net's CompareTo, the Sort expects a comparison of two objects to return a value of...

=0 -- if the objects are "equal"
<0 -- if the first object is "less than" the second
>0 -- if the first object is "greater than" the second

The Sort can then arrange the objects according to their comparisons,
BUT! Here it receives a "random" value between -0.5 and +0.5 -- thereby resulting in an unpredictably arranged sequence of objects.

Posted 27-Nov-17 14:44pm

PIEBALDconsult

Updated 27-Nov-17 15:01pm

v3

Comments

mappleleaf 27-Nov-17 21:23pm

Thank you so much Piebald for thelp. hmm So, .5 - Math.random(); is the same as Math.random() -.5 and that returns numbers between -.5 and +.5 right, but what is the purpose of passing an element in the function it it is not part of the random equation of '.5 - Math.random();'

PIEBALDconsult 27-Nov-17 21:33pm

Just to satisfy the requirement I suspect.