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rated 0 times [ 29] [ 7] / answers: 1 / hits: 130166 / 13 Years ago, thu, august 11, 2011, 12:00:00

What is the more efficient way to insert an array inside another array.

a1 = [1,2,3,4,5];

a2 = [21,22];



newArray - a1.insertAt(2,a2) -> [1,2, 21,22, 3,4,5];

Iterating a2 using splice looks a bit awfull from a performance point of view if a2 array is large.

Thanks.

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answered 13 Years ago donaldcristianl · Accepted Answer

You can use splice combined with some apply trickery:

a1 = [1,2,3,4,5];

a2 = [21,22];



a1.splice.apply(a1, [2, 0].concat(a2));



console.log(a1); // [1, 2, 21, 22, 3, 4, 5];

In ES2015+, you could use the spread operator instead to make this a bit nicer

a1.splice(2, 0, ...a2);