Concatenation of JS arrays

Concatenation of arrays

var a = [1,2,3,4,5,6];

var b=["foo", "Bar", "fun"];

The end result is:

[

1,2,3,4,5,6, "foo", "Bar", "Fun"

]

In general, the first thing we think about is concat.

C=a.concat (b);

C is a new array, at which time memory is used, c,a,b three arrays.

For large arrays?

The second way:

B "onto" a

for (Var i=0;i<b.length;i++) {

A.push (B.[i]);

}

B=null;

Obviously there is no new array creation, which is better for memory.

Notice the end of the b=null; After stitching is complete, array B is emptied

Do not like for loop can use the Third kind:

B "onto" a

A = B.reduce (function (Coll,item) {

Coll.push (item);

},A);

One more step to optimize

A.push.apply (A, b);

The writing of ES6

A.push (... b)

Concatenation of JS arrays