How to Generate Random String in JavaScript

1. Use the for Loop to Generate Random Strings
2. Use Built-In Methods to Generate Random Strings

This article will introduce multiple ways to generate random strings in JavaScript. Every method below will have a code example, which you can run on your machine.

Use the for Loop to Generate Random Strings

We use the Math.random() method to generate the random number between 0 and 1.

Math.floor(Math.random() * charactersLength) will generate a random number between 0 and the length of the declared array.

We use the for loop to create the required length of the random string. A random character is generated in each iteration.

Example:

const generateRandomString =
    (num) => {
      const characters =
          'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
      let result1 = ' ';
      const charactersLength = characters.length;
      for (let i = 0; i < num; i++) {
        result1 +=
            characters.charAt(Math.floor(Math.random() * charactersLength));
      }

      return result1;
    }

const displayRandomString =
    () => {
      let randomStringContainer = document.getElementById('random_string');
      randomStringContainer.innerHTML = generateRandomString(8);
    }

          console.log(generateRandomString(5));

Use Built-In Methods to Generate Random Strings

We can use the following built-in functions to generate random string:

• The Math.random() method to generate random characters.
• The toString(36) method representing [a-zA-Z0-9]. Read more about toString().
• The substring(startIndex, endIndex) method to return the specified number of characters.

Example

const generateRandomString =
    (num) => {
      const characters =
          'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
      let result1 = Math.random().toString(36).substring(0, num);

      return result1;
    }

             console.log(generateRandomString(7));