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Table of Contents
Using padStart()
Using padEnd()
Practical Use Cases
Home Web Front-end JS Tutorial How to use the padStart() and padEnd() string methods in JavaScript

How to use the padStart() and padEnd() string methods in JavaScript

Oct 11, 2025 am 03:41 AM

The padStart() and padEnd() methods add padding to strings without modifying the original. padStart() adds characters to the beginning, useful for formatting numbers or time, like "5".padStart(3, "0") yielding "005". padEnd() adds padding to the end, such as "Hello".padEnd(8, "!") producing "Hello!!!". Both methods accept a target length and an optional padding string, defaulting to spaces. They are ideal for aligning text, creating consistent IDs like "user".padEnd(8, "X") resulting in "userXXXX", or preparing data with leading/trailing characters. If the string meets or exceeds the target length, no padding is added. These methods return new strings, ensuring originals remain unchanged, offering a clean solution for string length control.

How to use the padStart() and padEnd() string methods in JavaScript

The padStart() and padEnd() methods in JavaScript are used to add padding to a string, ensuring it reaches a desired length. These methods don't modify the original string but return a new one with the added padding. They’re helpful for formatting text, aligning output, or preparing data like numbers with leading or trailing characters (e.g., adding zeros).

Using padStart()

The padStart(targetLength, padString) method adds characters to the beginning of a string until it reaches the specified length.

  • targetLength: The total length you want the resulting string to be.
  • padString (optional): The string to pad with. If not provided, a space is used by default.

Example:

let num = "5";
console.log(num.padStart(3, "0")); // "005"

let name = "Hi";
console.log(name.padStart(6, "*")); // "***Hi"

If the original string is already equal to or longer than the target length, no padding is added.

Using padEnd()

The padEnd(targetLength, padString) method works the same way as padStart(), but adds padding to the end of the string.

  • It also takes targetLength and an optional padString.
  • If padString is longer than needed, it gets truncated to fit.

Example:

let greeting = "Hello";
console.log(greeting.padEnd(8, "!")); // "Hello!!!"

let code = "AB";
console.log(code.padEnd(5, "0")); // "AB000"

Practical Use Cases

These methods are handy in real-world scenarios like:

  • Formatting time: "9".padStart(2, "0") → "09"
  • Creating consistent IDs: "user".padEnd(8, "X") → "userXXXX"
  • Aligning console output or table data with spaces

Basically, they offer a clean, built-in way to control string length with custom fillers. Just remember they return new strings—originals stay unchanged.

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