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)Copy

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 });Copy

Output:

{ result: '*' }
{ result: '***' }
{ result: '' }Copy

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);Copy

Output:

RangeError: Invalid count valueCopy

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);Copy

Output:

HiHiHiCopy

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.