apply方法

<script>
        //先演示apply函数使用
        function add(a, b) {
            return a + b + this.c;
        }
        let obj = {
                c: 520
            }
            // add.apply(obj,[10,20]);
        console.log(add.apply(obj, [10, 20])); //550


        //封装apply函数
        //原理：和call方法类似,但是apply方法的参数接收的是数组,所以接收参数的时候不用展开数组,调用Fn函数时再展开数组进行传参
        function apply(Fn, obj, args) {
            obj.temp = Fn;
            console.log(...args);
            let res = obj.temp(...args);
            delete obj.temp;
            return res;
        }

        function count(a, b) {
            return a + b + this.c;
        }
        let num = {
            c: 1314
        }
        console.log(apply(count, num, [10, 30])); //1354
    </script>