String.prototype.repeat()

Summary: in this tutorial, you’ll learn how to use the JavaScript string repeat() method to repeat a string a number of times.

Introduction to the JavaScript String repeat() method

The String.prototype.repeat() method returns a new string that repeats the original string a number of times.

Here’s the syntax of the repeat() method:

str.repeat(count)Code language: CSS (css)

In this method, the count is an integer that specifies the number of times to repeat the string str. The count is greater than 0 and less than +Infinity.

If the count is zero, the repeat() method returns an empty string. If the count is negative or +Infinity, the repeat() method raises a RangeError exception.

Note that the repeat() method doesn’t change the original string but returns a new string.

JavaScript String repeat() method examples

Let’s take some examples of using the repeat() method.

1) Basic JavaScript repeat() method example

The following example shows how to use the repeat() method:

let result = '*'.repeat(1);
console.log({ result });

result = '*'.repeat(3);
console.log({ result });

result = '*'.repeat(0);
console.log({ result });Code language: JavaScript (javascript)

Output:

{ result: '*' }
{ result: '***' }
{ result: '' }Code language: JavaScript (javascript)

2) JavaScript String repeat() method with negative count example

The repeat() method will raise a RangeError exception if you pass a negative count into the method. For example:

let result = '*'.repeat(-1);Code language: JavaScript (javascript)

Output:

RangeError: Invalid count valueCode language: JavaScript (javascript)

3) Using the repeat() method with a non-string object

The repeat() method is generic by design, which does not require its this value to be a String object. Therefore, you can use the repeat() method with any other objects. For example:

const message = {
  toString() {
    return 'Hi';
  },
};

const result = String.prototype.repeat.call(message, 3);
console.log(result);
Code language: JavaScript (javascript)

Output:

HiHiHi

Summary

• Use the repeat() method to repeat a string a number of times.
• The repeat() method is generic, which doesn’t require the this value to be a String object.