The difference between the each function and the map function in jquery

The use of each function and the map function in jquery looks similar, but there is a bit of a difference.

One important difference is that each returns an array of the original and does not create a new one. The map method returns a new array. If you use map without the need, it can be a waste of memory.

For example:

var items = [1,2,3,4]; $.each (items, function () {alert (' This was ' + this);}); var newitems = $.map (items, function (i) {return i + 1;}); NewItems is [2,3,4,5]

When you use each, the original items array is changed, and when you use map, you do not change items, just create a new array.

For example:

var items = [0,1,2,3,4,5,6,7,8,9]; var itemslessthanequalfive = $.map (items, function (i) {//Removes all items > 5 if (i > 5) return null; return i;} ); Itemslessthanequalfive = [0,1,2,3,4,5]

This is also true when an array is required for deletion, so it is quite serious to use each or map as a result of the deletion.

This article is from the "Liu Bofang blog" blog, make sure to keep this source http://liubofang.blog.51cto.com/11162557/1792460

The difference between the each function and the map function in jquery