javascript: generate 2 random but distinct numbers from range - Stack Overflow

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quick question:

What is the best way for implementing this line of python code (generates two random but distinct numbers from a given range)...

random.sample(xrange(10), 2)

...in Javascript?

Thanks in advance!

Martin

quick question:

What is the best way for implementing this line of python code (generates two random but distinct numbers from a given range)...

random.sample(xrange(10), 2)

...in Javascript?

Thanks in advance!

Martin

• javascript
• random
• sampling

Share Improve this question Follow asked Feb 9, 2011 at 14:53 HoffHoff 39.9k1717 gold badges8383 silver badges104104 bronze badges

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4 Answers 4

Sorted by: Reset to default 5

Here is my attempt using splice:

var a = [1,2,3,4,5,6,7,8,9,10];var sample = [];
sample.push(a.splice(Math.random()*a.length,1));
sample.push(a.splice(Math.random()*a.length,1));

Wrapped in a function:

function sample_range(range, n) {
  var sample = [];
  for(var i=0; i<n; i++) {
    sample.push(range.splice(Math.random()*range.length,1));
  }

  return sample;
}

var sample = sample_range([1,2,3,4,5,6,7,8,9,10], 2);

We could also stick the function into Array.prototype to have something like dot notation syntax:

Array.prototype.sample_range = function(n) {
    var sample = [];
    for(var i=0;i<n;i++) {
      sample.push(this.splice(Math.random()*this.length,1));
    }
    return sample;
};
var sample = [1,2,3,4,5,6,7,8,9,10].sample_range(2);

If you want to generate random numbers between 0 and n, one way is to randomly pick number r1 in 0..n then pick r2 from 0..n-1 and add 1 to r2 if r2 >= r1.

function sample(range,tot){
    if(tot > range){
        alert('infinite loop?');
        return [];
    }
    var myRandomNumbers = [];
    for(var i = 0; i<tot; i++){
        var randN = Math.floor(Math.random()*range);
        while(myRandomNumbers.contains(randN)){
            randN = Math.floor(Math.random()*range);
        }
        myRandomNumbers.push(randN);
    }
    return myRandomNumbers
}

var nums = sample(10,2); //array containing 2 distinct random numbers

Generate one, then repeatedly generate the second until it's not the same as the first. Tiny chance it will have to run longer, but you won't see any performance hit unless you need to generate billions of numbers.

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