js中数组API之foreach、map的用法

arr.forEach(function(value, index, array){……})

// forEach
var arr = [1,2,3,4,5];
arr.forEach(function(value, index, array){
    array[index] *= 2;    
});
console.log(arr);  //[2,4,6,8,10]

var newArr = arr.map(function(value, index, array){return 要放入新数组的值})

// map
var arr = [1,2,3,4,5];
var newArr = arr.map(function(value, index, array){
    return value * 2;
});
console.log(arr);  // [1,2,3,4,5]
console.log(newArr);  // [2,4,6,8,10]