<title>Document</title> <script> var arr=[1,2,3]; var arr1=[1,2,3,4,5,6]; arr.push(4); console.log(arr);//[1,2,3,4] arr.unshift(0); console.log(arr);//[0,1,2,3,4] arr.pop(); console.log(arr);//[0,1,2,3,] arr.shift(); console.log(arr);//[1,2,3] arr.splice(2,1,0); console.log(arr);//[1,2,0] //arr.join(); console.log(arr.join());//1,2,0 console.log(arr1.slice(2,4));//[3,4] console.log(arr.concat(arr1,[3,2,1])); //[1, 2, 0, 1, 2, 3, 4, 5, 6, 3, 2, 1] console.log(arr.indexOf(0));//2 console.log(arr.lastIndexOf(2));//1 var arr3=[1,5,6,99,52,663,22,66,552,6,622]; arr3.sort(function(a,b){ return a-b; }) console.log(arr3); // (11) [1, 5, 6, 6, 22, 52, 66, 99, 552, 622, 663] console.log(arr3.sort((a,b)=>a-b) ); // (11) [1, 5, 6, 6, 22, 52, 66, 99, 552, 622, 663] console.log(arr3.sort((a,b)=>b-a) ); //(11) [663, 622, 552, 99, 66, 52, 22, 6, 6, 5, 1] arr3.forEach(function(value,index){ console.log(index,value) })

    arr3.forEach((value,index)=>{console.log(index,value)})
    //0 663 1 622 2 552 3 99 4 66 5 52 6 22 7 6 8 6 9 5 10 1
    var newArr =arr3.filter(function(value,index){
        return value>100;       //筛选arr数组中值大于100的元素；
    })
    console.log(newArr);//(3) [663, 622, 552]


    var person = [
        {name: "张三",age:20,sex: "男"},
        {name: "李四",age:19,sex: "女"},
        {name: "王五",age:22,sex: "男"},
        {name: "赵六",age:21,sex: "女"}
    ];
    var x =person.filter(function(value,index){
    return value.age>20;           // 筛选出年龄大于20岁的学生
    // return value.sex=="男";     //筛选出男同学
    })
    console.log(x);/*0:{name: "王五", age: 22, sex: "男"}
                    1: {name: "赵六", age: 21, sex: "女"}
                    length: 2
                    __proto__: Array(0)*/
    var end = arr.map((value,index)=>value*2);
    //arr3=[663, 622, 552, 99, 66, 52, 22, 6, 6, 5, 1]
    console.log(end);//[2,4,0]
    var end=arr3.some(function(value,index){
    return value<500;
    });
    console.log(end);//true
    var end=arr3.every(function(value,index){
    return value<500;
    });
    console.log(end);//false
    console.log(arr3.reverse()); //(11) [1, 5, 6, 6, 22, 52, 66, 99, 552, 622, 663]


    var a={length:2,0:'aaa',1:'bbb'};  
    console.log(Array.from(a));//['aaa','bbb']
    var b={length:2};  
    console.log(Array.from(b));//[undefined.undefined]
    console.log(Array.of());// []
    console.log(Array.of(undefined));// [undefined]
    console.log(Array.of(1));// [1]
    console.log(Array.of(1,2,3,4,5) );// [1,2,3,4,5]
    var arr = [1,2,{name:"张三"}]
    console.log(arr.includes(2));// true
    console.log(arr.includes(4));// false
    console.log(arr.includes({name:"张三"}));// false
    console.log(['a','b','c','d'].includes('b')); // true
    console.log(['a','b','c','d'].includes('b', 1) );// true
    console.log(['a','b','c','d'].includes('b', 2) );// false
    console.log();
    console.log();
    var arr=[1,2,3,4,5,6,7,8,9];
    arr.sort(()=>Math.random()-0.5)
    console.log(arr);//乱序排列 刷新一次就不同
            
 

 
 

     



</script>