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 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

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