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JavaScript - String padStart() method example

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Created by:
Inayah-Alexander
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// ONLINE-RUNNER:browser;

const text = 'A';

console.log(text.padStart(1, '*')); // A
console.log(text.padStart(2, '*')); // *A
console.log(text.padStart(3, '*')); // **A

1. Documentation

Syntax

String padStart(maxLength)

String padStart(maxLength, fillString)

Parameters

maxLength- the lengthĀ ofĀ theĀ resultingĀ stringĀ onceĀ theĀ currentĀ stringĀ hasĀ beenĀ padded.

fillStringĀ -Ā TheĀ stringĀ toĀ padĀ theĀ currentĀ stringĀ with.

ResultA String of the specified maxLength with fillString applied from the start.
Description

The method pads the current string with a given string (possibly repeated) so that the resulting string reaches a given length. The padding is applied from the start (left) of the current string.

2. Practical example

In this example, we pad a number to keep only the last 3 digits.

// ONLINE-RUNNER:browser;

const number = '123456789';
const last3Digits = number.slice(-3);
const maskedNumber = last3Digits.padStart(number.length, '*');

console.log(maskedNumber);

Output:

******789

See also

  1. JavaScript - pad left number in string with zeros or spaces to get determined length

References

  1. String.prototype.padStart() - JavaScript | MDN

Alternative titles

  1. JavaScript - String.prototype.padStart() documentation with examples
  2. js - String padStart() method documentation with examples
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JavaScript - String (documentation)

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