item是数组的每一个元素, index是当前元素的索引值
1. [every]对数组中每一项运行以下函数,如果都返回true,every返回true,如果有一项返回false,则停止遍历 every返回false;
array.every(function(item,index,arr) {})
var arr=["关羽","狼人","张三丰","张无忌","5G","九尾狐"];
//arr是当前数组对象
var boo=arr.every(function(item,index,arr){
console.log(item,index);
console.log(arr);
return true;
})
console.log(boo);
打印台打印内容:
关羽 0
(6) [“关羽”, “狼人”, “张三丰”, “张无忌”, “5G”, “九尾狐”]
狼人 1
(6) [“关羽”, “狼人”, “张三丰”, “张无忌”, “5G”, “九尾狐”]
张三丰 2
(6) [“关羽”, “狼人”, “张三丰”, “张无忌”, “5G”, “九尾狐”]
张无忌 3
(6) [“关羽”, “狼人”, “张三丰”, “张无忌”, “5G”, “九尾狐”]
5G 4
(6) [“关羽”, “狼人”, “张三丰”, “张无忌”, “5G”, “九尾狐”]
九尾狐 5
(6) [“关羽”, “狼人”, “张三丰”, “张无忌”, “5G”, “九尾狐”]
true
var arr=["关羽","狼人","张三丰","张无忌","5G","九尾狐"];
var boo=arr.every(function(item,index,arr){
console.log(item);
if(item.length>2){
return false;
}
return true;
})
if(!boo){
console.log("数组不对,有超过两个的!!!");
}
打印台打印内容:
关羽
狼人
张三丰
数组不对,有超过两个的!!!
2. [filter]对数组中每一项运行以下函数,该函数返回结果是true的项,组成的新数组[ ];
var newArr=array.filter(function(item,index,arr){
console.log(arr);
});
var arr=["关羽","狼人","张三丰","张无忌","5G","九尾狐"];
var newArr=arr.filter(function(item,index,arr){
if(item.length>2){
return true;
}
return false;
})
console.log(newArr);
打印台打印内容:
(3) [“张三丰”, “张无忌”, “九尾狐”]
3.[forEach] 遍历数组,单纯的遍历数组,从头执行到尾 ,没有返回值;
array.forEach(function(item,index,arr){
console.log(item);
});
var arr=["关羽","狼人","张三丰","张无忌","5G","九尾狐"];
arr.forEach(function (item,index,arr){
console.log(item);
});
打印台打印内容:
关羽
狼人
张三丰
张无忌
5G
九尾狐
4. [map]对数组中每一项运行以下函数,该函数返回的结果组成的新数组;
var arr=array.map(function(item,index,arr){
return "\"" + item + "\"";
});
var arr=["关羽","狼人","张三丰","张无忌","5G","九尾狐"];
var newArr=arr.map(function(item,index,arr){
return item+"-->你好";
})
console.log(newArr);
打印台打印内容:
(6) [“关羽–>你好”, “狼人–>你好”, “张三丰–>你好”, “张无忌–>你好”, “5G–>你好”, “九尾狐–>你好”]
5. [some]对数组中每一项运行以下函数,如果该函数对某一项返回true,则some返回true;
var b=array.some(function(item,index,arr){
if (item == "ww"){
return true;
}
return false;
});
var arr=["关羽","狼人","张三丰","张无忌","5G","九尾狐"];
var boo=arr.some(function(item,index,arr){
console.log(item);
if(item.length>2){
return true;
}
});
if(boo){
console.log("数组有三个字的");
}
打印台打印内容:
关羽
狼人
张三丰
数组有三个字的