ES6 -- Application of expansion operator

 <script>
        var str = "abcdefg"
        //  Turn a string into an array 
        var arr = str.split("")
        console.log(arr);
        // ES6 Extension operators 
        var arr1 = [...str]
        console.log(arr1);

        let arr2 = [1, 2, 2, 3, 3, 4, 5]
        let s = new Set(arr2) // It's an array of classes 

        //  hold Set Class array to true array 
        let news = Array.from(s)
        console.log(news);
        //  Extended operator implementation set Turns into a real array 
        let newss = [...s]
        console.log(newss);
        //  You can't use the following methods , hold set Set to array 
        Array.prototype.slice.call(s)

        //  How to splice arrays 
        let aa1 = [1, 2, 3];
        let aa2 = [4, 5, 6];
        // concat-- Splicing 
        let newaa = aa1.concat(aa2)
        console.log(newaa);
        //  Expand operator splicing 
        let newaa2 = [...aa1, ...aa2]
        console.log(newaa2);

        //  Put the passed parameters , Make an array 
        //  Traditional solutions 
        function fn() {
            console.log(Array.prototype.slice.call(arguments));
        }
        fn(1, 2, 3, 4, 5)

        // es6 How to solve  
        function fn(...a) {
            // console.log([...arguments]);
            console.log(a);
        }
        fn(1, 2, 3, 4, 5)

        //  The first parameter needs to use , Other composition array 
        function fn(z, ...a) {
            // console.log([...arguments]);
            console.log(z, a);
        }
        fn(1, 2, 3, 4, 5)
    </script>