Usage of const in js

In JavaScript, const is used to declare constant variables whose values ​​cannot be reassigned while the program is running. Purposes include: 1) preventing variables from being reassigned; 2) identifying immutable constants. The syntax is: const variableName = value.

Usage of const in JavaScript

In JavaScript, the const keyword is used Declare constant variables. The value of a constant variable cannot be reassigned while the program is running.

Main purpose

• Prevent variable reassignment: Using const to declare variables can prevent accidental changes, thus Improve code robustness.
• Identifying constants: Values ​​declared using const typically represent immutable constants, such as mathematical constants (e, π) or application configuration options.

Syntax

<code class="javascript">const variableName = value;</code>

Where:

• variableName:To be declared The name of the constant variable.
• value: The value to be assigned to the constant.

Note

• Constant variables must be initialized when declared.
• The value of a constant variable cannot be reassigned.
• Constant variables cannot be declared as objects or arrays, but constant variables can be assigned to objects or arrays.
• Constant variables are usually named with all uppercase letters to indicate their constant nature.

Example

<code class="javascript">// 声明一个数学常数
const PI = 3.14159;

// 声明一个应用程序配置选项
const APPLICATION_NAME = "My Application";

// 声明一个不可变对象
const person = {
  name: "John Doe",
  age: 30
};</code>

In the above example, PI, APPLICATION_NAME and person are constant variables, and their values ​​cannot be modified while the program is running.

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