全面解析JavaScript里的循环方法之forEach，for-in，for-of

for (var index = 0; index < myArray.length; index++) {
console.log(myArray[index]);
}

myArray.forEach(function (value) {
console.log(value);
});

var obj = {a:1, b:2, c:3};
for (var prop in obj) {
console.log("obj." + prop + " = " + obj[prop]);
}
// 输出:
// "obj.a = 1"
// "obj.b = 2"
// "obj.c = 3"

for (var index in myArray) { // 不推荐这样
console.log(myArray[index]);
}

for (var value of myArray) {
console.log(value);
}

let iterable = [10, 20, 30];
for (let value of iterable) {
console.log(value);
}
// 10
// 20
// 30

let iterable = [10, 20, 30];
for (const value of iterable) {
console.log(value);
}
// 10
// 20
// 30

let iterable = "boo";
for (let value of iterable) {
console.log(value);
}
// "b"
// "o"
// "o"
let iterable = new Uint8Array([0x00, 0xff]);
for (let value of iterable) {
console.log(value);
}
// 0
// 255
let iterable = new Map([["a", 1], ["b", 2], ["c", 3]]);
for (let [key, value] of iterable) {
console.log(value);
}
// 1
// 2
// 3
for (let entry of iterable) {
console.log(entry);
}
// [a, 1]
// [b, 2]
// [c, 3]
let iterable = new Set([1, 1, 2, 2, 3, 3]);
for (let value of iterable) {
console.log(value);
}
// 1
// 2
// 3

// Note: This will only work in platforms that have
// implemented NodeList.prototype[Symbol.iterator]
let articleParagraphs = document.querySelectorAll("article > p");
for (let paragraph of articleParagraphs) {
paragraph.classList.add("read");
}

for (var key of Object.keys(someObject)) {
console.log(key + ": " + someObject[key]);
}

function* fibonacci() { // a generator function
let [prev, curr] = [0, 1];
while (true) {
[prev, curr] = [curr, prev + curr];
yield curr;
}
}
for (let n of fibonacci()) {
console.log(n);
// truncate the sequence at 1000
if (n >= 1000) {
break;
}
}