How to generate a random unique ID with JavaScript

  • Post category:JavaScript
  • Reading time:5 mins read

Generating a random unique ID is a common requirement in many JavaScript applications. This unique ID can be used for various purposes, such as assigning a unique identifier to a new item in a list, creating a unique key for a React component, generating a unique URL or filename, and many others.

There are several ways to generate a random unique ID in JavaScript, but the most common approach is to use the built-in Math.random() method to generate a random number and then convert it into a unique ID. However, this approach has some limitations, as it may generate duplicate IDs, which can cause issues in some scenarios.

To generate a truly unique ID, we need to ensure that it has never been generated before. One way to achieve this is to use a combination of current timestamp and a random number to generate a unique ID. This approach guarantees that the ID will be unique, as it is based on the current time, which is always changing.

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Let’s take a look at some examples of how to generate a random unique ID in JavaScript:

Method 1: Using Math.random() function

The Math.random() function returns a random floating-point number between 0 and 1. We can use this function to generate a random number and convert it into a unique string. The following code snippet demonstrates this method:

function generateUniqueId() {
  const randomNum = Math.random().toString(36).substr(2, 9);
  return randomNum;
}

console.log(generateUniqueId()); // e.g. "8jz6hf9k2"

In the above code snippet, we are calling the Math.random() function to generate a random floating-point number. We then convert this number to a string using the toString() method and specify a base of 36. This converts the number to a string of alphanumeric characters. We then use the substr() method to extract a substring of length 9, starting from index 2. This ensures that we get a unique string of length 9 characters.

Method 2: Using the Date.now() function

The Date.now() function returns the current timestamp in milliseconds. We can use this function to generate a unique ID by concatenating the current timestamp with a random number. The following code snippet demonstrates this method:

function generateUniqueId() {
  const randomNum = Math.floor(Math.random() * 1000);
  const timestamp = Date.now();
  return `${timestamp}${randomNum}`;
}

console.log(generateUniqueId()); // e.g. "1644808765154-285"

In the above code snippet, we are calling the Math.floor() function to round down a random number between 0 and 999. We then get the current timestamp using the Date.now() function and concatenate it with the random number to generate a unique ID.

Method 3: Using the uuid library

The uuid library is a popular package for generating unique IDs in JavaScript. It provides a variety of methods for generating different types of unique IDs. To use the uuid library, we need to install it using npm or yarn:

npm install uuid

Once installed, we can import the library and use its methods to generate unique IDs. The following code snippet demonstrates this method:

import { v4 as uuidv4 } from 'uuid';

function generateUniqueId() {
  return uuidv4();
}

console.log(generateUniqueId()); // e.g. "2f9fc7e0-6c0d-4d6c-b682-7f8e31d0d41e"

In the above code snippet, we are importing the v4 method from the uuid library, which generates a random unique ID. We then call the uuidv4() function to generate a unique ID.

Conclusion:

Generating unique IDs is an important task in web development. In this article, we explored three popular methods for generating random unique IDs in JavaScript. The Math.random() method, the Date.now() method, and the uuid library are all great options for generating unique IDs. Depending on your specific needs, you can choose the method that best fits your use case.

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