JavaScript中三种for循环语句的使用总结（for、for...in、for...of）

const array = [4, 7, 9, 2, 6];
for (let index = 0; index < array.length; index++) {
    const element = array[index];
    console.log(element);
}
// 4, 7, 9, 2, 6

const temp = {name: "temp"};
function Apple() {
    this.color = 'red';
}

Apple.prototype = temp;

const obj = new Apple();

for (const prop in obj) {
    console.log(`obj.${ prop } = ${ obj[prop] }`);
}

// obj.color = red
// obj.name = temp

const temp = {name: "temp"};
function Apple() {
    this.color = 'red';
}

Apple.prototype = temp;

const obj = new Apple();

for (const prop in obj) {
    if (obj.hasOwnProperty(prop)) {
        console.log(`obj.${ prop } = ${ obj[prop] }`);
    }
}

// obj.color = red

const arr = [1, 2, 3, 4, 5];
for (const key in arr) {
    console.log(key)
}
// 0,1,2,3,4

const array = ['a', 'b', 'c'];
for (const element of array) {
    console.log(element);
}

// a
// b
// c

Object.prototype.objCustom = function () { };
Array.prototype.arrCustom = function () { };

let iterable = [3, 5, 7];
iterable.foo = 'hello';

for (const key in iterable) {
    console.log(key); // logs 0, 1, 2, "foo", "arrCustom", "objCustom"
}
// 0, 1, 2, "foo", "arrCustom", "objCustom"

for (const key of iterable) {
    console.log(key);
}
// 3, 5, 7

let nodes = new Map();
nodes.set("node1", "t1")
    .set("node2", "t2")
    .set("node3", "t3");

for (const [node, content] of nodes) {
    console.log(node, content);
}
// node1 t1
// node2 t2
// node3 t3