Question

86

How to toggle an element in array using JavaScript?

rated 0 times [ 93] [ 7] / answers: 1 / hits: 52928 / 11 Years ago, mon, june 17, 2013, 12:00:00

Here is my code for javascript for this simple task:

Remove the element if it exists in an array.

Add the element if it is not in an array.

if(_.contains(this.types,type_id)){

    var index = this.types.indexOf(type_id);

    this.types.splice(index,1);

}

else{

    this.types.push(type_id);

}

Is there a more efficient way to do this?

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simone

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2 Years ago

answered 11 Years ago brodyfrancisi · Accepted Answer

If you care about efficiency then may be using an array to implement a set is a bad idea. For example using an object you could do:

function toggle(S, x) {

    S[x] = 1 - (S[x]|0);

}

then after many add/remove operations you can keep only keys where the value is 1

This way every addition/removal is O(1) and you need only one O(n) operation to get the final result.

If keys are all small numbers may be a bitmask is even worth the effort (not tested)

function toggle(S, x) {

    var i = x >> 4;

    S[i] = (S[i]|0) ^ (1<<(x&15));

}