javascript----ECMScript 6

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<head>
    <title>javascript---ECMScript 6 第一阶段</title>

<meta name='discription' content="javascript---ECMScript 6 ">

</head>

<body>
    <script type="text/javascript">
    //1、解构赋值  字符串->字符
    const [a, b, c, d, e] = "abcde";
    alert(a); // a



    //2、数值数组 -> 数值
    var [a, b, c] = [1, 2, 3];
    alert(a); //a



    //3、解构赋值
    var [foo, [
        [bar], baz
    ]] = [1, [
        [2]
    ], 3];
    alert(foo); // 1



    // 4、解构赋值->互换数值
    var x = 10;
    var y = 15;

    alert("x" + x + ",y" + y); //x:10,y:15

    [x, y] = [y, x];

    alert("x" + x + ",y" + y); // x:15,y:10



    //5、map 的赋值遍历
    var map = new Map();
    map.set("first", "hello");
    map.set("second", "world");

    for (var [key, value] of map) {
        console.log(key + ' is ' + value);
    }


    //6、Symbol 类型 ： 一个类似字符串的新数据类型
    var s1 = Symbol("foo");
    var s2 = Symbol("bar");
    console.log(typeof(s1));


    //7、ArrayBuffer对象 ： 代表存储二进制数据的一段内存，不能直接读写
    var buf = new ArrayBuffer(32);
    var dataView = new DataView(buf);
    var da = dataView.getUint8(0);
    console.log(da);




    //8、读取arraybuffer 对象内容
    var buffer = new ArrayBuffer(12);
    var x1 = new Int32Array(buffer);
    x1[0] = 1;
    var x2 = new Int32Array(buffer);
    x2[0] = 2;
    console.log(x1);



    //9、二进制数组的应用
    var xhr = new xmlHttpRequest();
    xhr.open("get", url);
    xhr.responseType = "arrayBuffer";
    xhr.onload = function() {
        let arrayBuffer = xhr.response;
    }
    onreadystatechange = function() {
        if (req.readyState === 4) {
            var arrayResponse = xhr.response;
            var dataView = new DataView(arrayResponse);
            var ints = new Uint32Array(dataView.byteLength / 4);

            xhrDiv.style.backgroundColor = "red";
            xhrDiv.innerText = "Array is " + ints.length + "uints long";

        }
    }






    //10、set数据结构，类似数组，但是成员的值是唯一的
    var s = new Set();
    [2, 3, 4, 5, 6, 7, 2, 3, 4].map(x => s.add(x));
    for (let i in s) {
        console.log(i);
    }






    //11、 set赋值
    var set = new Set([1, 2, 1, 2, 5, 6, 7]);
    console.log(set.length); // 还不支持
    for (let i in set) {
        console.log(i);
    }



    //12、map,set
    var m = new Map();
    var o = { "p": "Hello World!" };

    console.log(o); // {p:"Hello World!"}

    m.set(o, "content");

    console.log(m.get(o)); //content



    //13、菱形 
    document.write("<h1>8</h1>");
    var n = 5;

    for (var i = 0; i < 2 * n - 1; i++) {
        if (i < n) {
            for (var j = 0; j < 2 * n - 1; j++) {
                if (j == n - i - 1 || j == n + i - 1) {
                    document.write("蓝");
                } else {
                    document.write("一");
                }
            }
            document.write("</br>");

        } else {
            for (var j = 0; j < 2 * n - 1; j++) {
                if (j == i - n + 1 || j == 3 * n - i - 3) {
                    document.write("蓝");
                } else {
                    document.write("一");
                }
            }
            document.write("</br>");
        }
    }
    </script>
</body>

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