Apply method don't have him!

The first is apply () a very powerful function-- can be an array by default into a parameter list!!!

Application:

1. Find the maximum value in an array

var arr= [1, 3, 3, 6];    var max =math.max.apply (null, arr);    Alert (max);    6   

The Math.max () method accepts multiple arguments, but does not accept the array, so the direct Math.max (arr) is not able to achieve the effect, and the array is converted to the parameter list by apply ().

2. Merging arrays

① using the Concat () method

var arr1 = [1, 3, 3, 6];    var arr2 = [2, 4, 5, 6];    var arr = Arr1.concat (arr2); alert (arr);//[1,3,3,6,2,4,5,6]    

The concat () method does not change the original array, only a new array is returned.

② Loop Traversal Insert

var arr1 = [1, 3, 3, 6];     var arr2 = [2, 4, 5, 6];     var arr2len = arr2.length;      for (var i=0; i<arr2len; i++) {        arr1.push (arr2[i]);    }    alert (arr1);    [1,3,3,6,2,4,5,6] 

③apply () method

var arr1 = [1, 3, 3, 6];     var arr2 = [2, 4, 5, 6];     var arr =  Array.prototype.push.apply (arr1, arr2);    Alert (arr);      8    alert (arr1);     [1,3,3,6,2,4,5,6] 

Inserts the contents of the ARR2 directly into the arr1, and the expression return value is the length of the array.

Apply method don't have him!