Does JavaScript support constants?

Other Questions JavaScript
1

Is there a method to implement constants in JavaScript? If constants aren’t available, what is the usual approach for defining variables intended to be constant?

2

You can define constants in JavaScript using the const keyword, which prevents reassignment. For immutability in objects, leverage Object.freeze().

const URL = 'https://example.com';

A creative approach is using ES6 template literals to create constant-like behavior, securing your constants within strings or lists:

const KEYS = `API_KEY: your-api-key`, `TOKEN: your-token`;
3

In JavaScript, you can define constants using the const keyword. This ensures the variable cannot be reassigned. Here's an example:

const PI = 3.14;

Use Object.freeze() for true immutability in objects:

const CONFIG = Object.freeze({ key1: 'value1' });
4

In addition to using the const keyword, JavaScript provides certain patterns and features to ensure variables intended to act as constants remain unchanged. One of these techniques is using a getter to encapsulate the value. This approach can be particularly useful when defining constants within objects or modules:

const constants = {
  get PI() {
    return 3.14;
  },
  get MAX_USERS() {
    return 100;
  }
};

console.log(constants.PI); // 3.14
console.log(constants.MAX_USERS); // 100

The getter approach ensures that these values are read-only, effectively behaving as constants. This method is beneficial when you require constants as part of larger collections or configurations, enhancing code readability and maintaining integrity.

Furthermore, for more complex constant-like patterns, consider the module pattern to encapsulate and enforce immutability where necessary. By doing so, you can structure your code to prevent reassignment and accidental modifications, aligning closely with best practices in software development.

5

Yes, JavaScript supports constants using the const keyword. This keyword is perfect for variables that you don't want to reassign. Here's how you can define a constant:

const API_KEY = 'your-api-key-here';

Using const only prevents reassignment, not mutation. For true immutability, particularly for objects or arrays, consider combining with Object.freeze() to prevent any modification to the object's properties:

const SETTINGS = Object.freeze({
  theme: 'dark',
  version: '1.0',
});

By doing so, any attempt to change the properties of SETTINGS will be ignored in strict mode. This approach ensures efficiency in maintaining an unmodifiable set of values, crucial for configurations and constant definitions in complex applications.