For of/for in的区别

"for of"和"for in"都是JavaScript中的迭代器，但它们的用途不同。

"for of"用于迭代可迭代对象的值，例如数组、字符串等。

例如：

const arr = [1, 2, 3];

for (const value of arr) {
  console.log(value); // 1, 2, 3
}

const str = "hello";

for (const char of str) {
  console.log(char); // h, e, l, l, o
}

"for in"用于迭代对象的属性名称，例如对象的键。

例如：

const obj = {a: 1, b: 2, c: 3};

for (const key in obj) {
  console.log(key); // a, b, c
}

需要注意的是，"for in"迭代的是对象的属性名称，而不是属性的值。因此，如果需要获取属性的值，需要使用对象的[key]语法。

例如：

const obj = {a: 1, b: 2, c: 3};

for (const key in obj) {
  console.log(obj[key]); // 1, 2, 3
}

相关问题

for in/for of

`for in` and `for of` are both loops used in JavaScript for iteration, but they have different use cases and syntax.

`for in`:
The `for in` loop is used for iterating over the properties of an object. It is generally used with objects, and not with arrays or strings. The syntax of `for in` is:

for (variable in object) {
  // code to be executed
}

Here, `variable` represents a property name of the object, and `object` is the object being iterated. The loop will iterate over all the enumerable properties of the object, including those inherited from its prototype chain.

Example:

const person = {
  name: 'John',
  age: 30,
  gender: 'male'
};

for (let property in person) {
  console.log(`${property}: ${person[property]}`);
}

// Output:
// name: John
// age: 30
// gender: male

`for of`:
The `for of` loop is used for iterating over the values of an iterable object, such as an array or a string. The syntax of `for of` is:

for (variable of iterable) {
  // code to be executed
}

Here, `variable` represents the value of each element in the iterable, and `iterable` is the iterable object being iterated. The loop will iterate over all the elements of the iterable, in the order they appear.

Example:

const colors = ['red', 'green', 'blue'];

for (let color of colors) {
  console.log(color);
}

// Output:
// red
// green
// blue

In summary, `for in` is used for iterating over properties of an object, while `for of` is used for iterating over values of an iterable object.

for of和for in区别

for...in和for...of都是用来遍历的属性，但是它们有以下区别：

共性：
- 都可以遍历数组和对象

区别：
- for...in语句用于遍历对象的属性，而for...of语句用于遍历可迭代对象的元素
- for...in语句返回的是对象的键名，而for...of语句返回的是对象的键值
- for...in语句可以遍历对象的原型链上的属性，而for...of语句不行
- for...in语句可以遍历字符串类型的键名，而for...of语句不行

以下是两个例子来说明它们的区别：

1. 遍历对象

const obj = { a: 1, b: 2, c: 3 }

// for...in语句遍历对象的属性
for (let i in obj) {
  console.log(i) // 输出：a b c
}

// for...of语句不能用于对象
for (let i of obj) {
  console.log(i) // 输出：Uncaught TypeError: obj is not iterable 报错了
}

2. 遍历数组

const arr = [1, 2, 3]

// for...in语句遍历数组的下标
for (let i in arr) {
  console.log(i) // 输出：0 1 2
}

// for...of语句遍历数组的元素
for (let i of arr) {
  console.log(i) // 输出：1 2 3
}