06-Array的扩展方法

一、from()

    <script>
        //伪数组转数组
        var obj = {
            "0": 'zs',
            "1": 20,
            length: 2
        }
        let newArray = Array.from(obj, item => item * 2)
        console.log(newArray); //[NaN,40]
    </script>

二、find()

   <script>
        //find()用于找出第一个符合条件的数组成员 如果没有找到返回undefined
        let arr = [{
            id: 1,
            name: '张三'
        }, {
            id: 2,
            name: '李四'
        }, {
            id: 3,
            name: '张'
        }];
        let target = arr.find((item, index) => item.id = 2)
        console.log(target);
    </script>

三、findIndex()

    <script>
        //用于找出第一个符合条件的数组成员位置 没有返回-1
        let arr = [1, 5, 10, 15]
        let index = arr.findIndex((value, index) => value > 9)
        let index2 = arr.findIndex((value, index) => value > 20)
        console.log(index);
        console.log(index2);
    </script>

四、includes()

    <script>
        //includes() 表示某个数组是否包含给定的值 返回是一个布尔值
        let arr = [1, 2, 3]
        console.log(arr.includes(4));
        console.log(arr.includes(2));
    </script>