JavaScript: For , For/in , For/of

 For:

define：

The for statement can customize how many times you want to execute code

Grammar：

　　for (condition 1; condition 2; condition 3)
　　{
   　　　　 code
　　} 

Condition explain:

condition	describe
1	prestart before beginning.
2	loop condition.
3	Execute after the loop has been executed.

Example：

for (var i=0; i<5; i++)
{
      x=x + "The number is " + i + "<br>";
}

The code 's output:

　　　　The number is 0
　　　　The number is 1
　　　　The number is 2
　　　　The number is 3
　　　　The number is 4

---

For/in:

define：

The for/in statement is used to loop through the object properties。

Grammar：

　　for (var in object) {
　　　　 code
　　}

parameter values:

parameter	describe
var	Must.variable can be an array element or an attribute of an object. (指定的变量可以是数组元素，也可以是对象的属性。)
object	Must.Object that specifies the iteration. (指定迭代的的对象。)

Example：

var string = {lesson:"web", verb:"is", describe:"fun"}; 

var text = "";
var x;
for (x in string) {

    text += string[x]+" ";
}

The code 's output:

　　　　web is fun 

---

For/of:

define：

The for/of statements creates a loop iterating over iterable objects.

Grammar：

　　for (variable of iterable) {
　　  　　statement
　　}

parameter values:

parameter	describe
variable	On each iteration a value of a different property is assigned to variable. (在每次迭代中，将不同属性的值分配给变量。)
object	Object whose iterable properties are iterated. (被迭代枚举其属性的对象。)

Example：

let iterable = [10, 20, 30];

for (let value of iterable) {
    value += 1;
    console.log(value);
}

The code 's output:

　　　　11 21 31

---

 Related Pages:

JavaScript for    :          http://www.runoob.com/js/js-loop-for.html

JavaScript for/in :         http://www.runoob.com/jsref/jsref-forin.html 

MDN - for...of :              https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Statements/for...of

Javascript statement :   http://www.runoob.com/jsref/jsref-statements.html