JavaScript for...in 循环

迭代（循环）对象的属性：

const person = {fname:"John", lname:"Doe", age:25};
let text = "";
for (let x in person) {
text += person[x] + " ";
}

迭代（循环）数组的值：

const cars = ["BMW", "Volvo", "Saab", "Ford"];
let text = "";
for (let x in cars) {
text += cars[x] + " ";
}

下面有更多示例。

描述

这个for...in语句组合迭代（循环）对象的属性。

循环内的代码块针对每个属性执行一次。

如果索引顺序很重要，请勿使用 for...in 来迭代数组。请改用 for 循环。

for (x in object) {
code block to be executed
}

Parameter	Description
x	Required. A variable to iterate over the properties.
object	Required. The object to be iterated

for...in是 ECMAScript1 (ES1) 功能。

所有浏览器均完全支持 ES1 (JavaScript 1997)：


Chrome	Edge	Firefox	Safari	Opera	IE
Yes	Yes	Yes	Yes	Yes	Yes