Create a String of length N filled with repeated char in JS

# Create a String of length N filled with repeated char in JS

Use the String.repeat() method to create a string of variable length.

The String.repeat() method takes the string that should be repeated as a parameter and repeats the string the specified number of times.

index.js

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const str = 'a'.repeat(3);

console.log(str); // 👉️ 'aaa'

create string of length n filled with repeated char

The code for this article is available on GitHub

The argument we passed to the String.repeat() method is the number of times the string should be repeated.

index.js

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console.log('a'.repeat(3)); // 👉️ aaa
console.log('a'.repeat(4)); // 👉️ aaaa
console.log('a'.repeat(5)); // 👉️ aaaaa

console.log('abc-'.repeat(2)); // 👉️ abc-abc-
console.log('abc-'.repeat(3)); // 👉️ abc-abc-abc-

The method returns a new string, containing the specified number of repetitions of the string it was called on.

Alternatively, you can use the Array() constructor.

# Create a String of Variable Length using the Array() constructor

This is a two-step process:

Use the Array() constructor to create an array of empty elements of length N + 1.
Use the join() method to join the array with the string to be repeated.

index.js

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const arr = Array(3 + 1);
console.log(arr); // 👉️ [ , , , ]

const str = arr.join('a');
console.log(str); // 👉️ aaa

create string of variable length using array constructor

The code for this article is available on GitHub

We used the Array constructor to create an array, filled with 4 empty elements.

index.js

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const arr = Array(3 + 1);

// 👇️ [ <4 empty items> ]
console.log(arr); // 👉️ [ , , , ]

The reason I added 1 to the desired length of the array is that we later use the Array.join() method to join the array elements with the specified string as the separator.

index.js

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const arr = Array(3 + 1);
console.log(arr); // 👉️ [ , , , ]

const str = arr.join('a');
console.log(str); // 👉️ aaa

An easy way to think about it is - the number of commas in the array is how many repetitions you'll get when you call the Array.join() method.

Our array consists of 4 empty elements, so the string we passed to the Array.join() method gets repeated 3 times.

# Additional Resources

You can learn more about the related topics by checking out the following tutorials:

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Create a String of length N filled with repeated char in JS