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What is the fastest or most elegant way to compute a set difference using Javascript arrays?

rated 0 times [ 126] [ 3] / answers: 1 / hits: 120843 / 15 Years ago, thu, november 12, 2009, 12:00:00

Let A and B be two sets. I'm looking for really fast or elegant ways to compute the set difference (A - B or A B, depending on your preference) between them. The two sets are stored and manipulated as Javascript arrays, as the title says.

Notes:

Gecko-specific tricks are okay

I'd prefer sticking to native functions (but I am open to a lightweight library if it's way faster)

I've seen, but not tested, JS.Set (see previous point)

Edit: I noticed a comment about sets containing duplicate elements. When I say set I'm referring to the mathematical definition, which means (among other things) that they do not contain duplicate elements.

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wilson

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answered 15 Years ago felixa · Accepted Answer

I don't know if this is most effective, but perhaps the shortest:

var A = [1, 2, 3, 4];

var B = [1, 3, 4, 7];



var diff = A.filter(function(x) {

  return B.indexOf(x) < 0;

});



console.log(diff); // [2]

Updated to ES6:

const A = [1, 2, 3, 4];

const B = [1, 3, 4, 7];



const diff = A.filter(x => !B.includes(x));



console.log(diff); // [2]