ES5中Array新增加的API接口 forEach map filter some every indexOf lastIndexOf reduce reduceRight

var array = [23,48,66,2];

  forEach:循环、遍历数组；没有返回值。与for循环类似 
array.forEach(function( value, index, array ) {
  console.log(value);
  return value *  value;
} );

  map:映射的意思，映射返回一个新数组，有返回值;filterArr:返回一个新对象 
var mapArr = array.map(function(value, index, array ){
 return value *  value;
});

  filter:过滤、筛选的意思; 有返回值; filterArr:返回过滤后新数组 
var filterArr = array.filter(function(value, index, array ) {
  if ( value > 20 ) {
    return true;
  }
  return false;
});

  everyArr:每一个、每一项意思; 有返回值; every:返回boolean  true or false; 
var everyArr = array.every(function(value, index, array){
  if ( value > 1 ) {
    return true;
  }
});

 indexOf:第一个是检索的值，第二个是需要检索的位置从0开始 
console.log(array.indexOf(23,0));

  lastIndexOf:第一个是检索的值，第二个是需要检索的位置从arr.length-1开始的 
console.log(array.lastIndexOf(2,10));

// 初始设置 previous = initialValue = 1, current = 2 

// 第一次迭代 previous = (1 + 2) =  3, current = 3 

// 第二次迭代 previous = (3 + 3) =  6, current = 4 

// 第三次迭代 previous = (6 + 4) =  10, current = undefined (退出) 
var reduce = [1,2,3,4].reduce(function(prev, curr, index, array) {
  console.log(prev +"  "+ curr);
  return prev + curr;
});

// 初始设置 index = 3, previous = initialValue = 4, current = 3 

// 第一次迭代 index = 2, previous = (4- 3) = 1, current = 2 

// 第二次迭代 index = 1, previous = (1 - 2) = -1, current = 1 

// 第三次迭代 index = 0, previous = (-1 + 1) = 0, current = undefined (退出) 
var reduceRight = [1,2,3,4].reduceRight(function(prev, curr, index, array) {
  if ( index == 0 ) {
    return prev + curr;
  }
  return prev - curr;
});

console.log(reduceRight);

ES5中Array新增加的API接口 forEach map filter some every indexOf lastIndexOf reduce reduceRight

原文：http://blog.csdn.net/itpinpai/article/details/50012173