javascript----ECMScript 6
<!DOCTYPE html>
<html>
<head>
<title>javascript---ECMScript 6 第一阶段</title>
<meta name="keyword" content="javascript---ECMScript 6 ">
<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>
</html>
