The role of const in js

const defines a constant variable in JavaScript, its value is determined at compile time and cannot be reassigned. Its benefits include enhanced reliability, improved readability, and optimized performance. When using const, you need to assign a value at the time of declaration. Use uppercase or underscore to indicate constants, but references pointing to constant variables can be reassigned.

The role of const in JavaScript

In JavaScript, const is a keyword used to declare constants variable. The value of a constant variable is determined at compile time and cannot be reassigned during program execution.

Use of const

Using const to declare constant variables has the following benefits:

• Enhance code reliability: Since the value of a constant variable cannot be changed, errors caused by accidental assignments are avoided.
• Improve the readability of the code: The const declaration clearly indicates that the variable is a constant, which helps to understand the intent of the code.
• Optimize performance: Since the value of a constant variable is fixed, the JavaScript engine can be optimized to reduce memory allocation and value lookups.

Usage rules of const

When using const to declare constants, you need to comply with the following rules:

• Constant variables must be declared time assignment.
• The value of a constant variable cannot be reassigned.
• The names of constant variables are usually in the format of words separated by uppercase letters or underscores to indicate their constant nature.

Example

<code class="javascript">const PI = 3.14159;
const MAX_SIZE = 100;</code>

Note:

Although the value of a variable declared by const cannot be reassigned, it points to The reference to this variable can be reassigned. For example:

<code class="javascript">const object = { name: "John Doe" };
object.name = "Jane Doe"; // 这是允许的，因为object指向另一个对象</code>

This does not change the variable object declared by const, but changes the object referenced by object.

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