数组扩展

1. Array.from(v) : 将伪数组对象或可遍历对象转换为真数组

<body>
     <div>div1</div>
     <div>div2</div>
     <div>div3</div>
        <br>
        <script>
            let divs = document.getElementsByTagName('div');
             var arrDiv='' 
             Array.from(divs).forEach(function (item, index) {
                
                console.log(item, index);
    })
           
        </script>
</body>

2. Array.of(v1, v2, v3) : 将一系列值转换成数组

let arr = Array.of(1, 'abc', true);

console.log(arr instanceof Array);//true

3. find(function(value, index, arr){return true}) : 找出第一个满足条件返回true的元素

     let arr1 = [1,3,5,2,6,7,3];
    let result = arr1.find(function (item, index) {
        return item >3
    });
    console.log(result);//5

4 findIndex(function(value, index, arr){return true}) : 找出第一个满足条件返回true的元素下标

 let arr1 = [1,3,5,2,6,7,3];
let result1 = arr1.findIndex(function (item, index) {
        return item >3
    });
    console.log(result1);//2

5 findIndex(function(value, index, arr){return true}) : 找出第一个满足条件返回true的元素下标

    let arr1 = [1,3,5,2,6,7,3];   
 let result1 = arr1.findIndex(function (item, index) {
        return item >3
    });
    console.log(result1);//2