JS: String.prototype.padStart

By Xah Lee. Date: . Last updated: .

New in ES2017.

Return a new string, by adding padStr to the left of string str so the length is n.

padStr is space by default.

Example:

console.log ( "x".padStart(3) === "  x"); // true

console.log ( "x".padStart(3, "0") === "00x"); // true

console.log ( "x".padStart(4, "ab") === "abax"); // true

Note, when the string contains NON-ASCII character, result may not be expected.

[see JS: Character, Code Unit, Codepoint]

console.log ( "😂".padStart(2,"x") === "😂" );
// no padding happens, because "😂" is already length 2

// 😂
// name: FACE WITH TEARS OF JOY
// codepoint decimal: 128514
// codepoint hexadecimal: 1f602
// UTF8 encoding: F0 9F 98 82
// Utf16 encoding: D8 3D DE 02

JS String

  1. String Overview
  2. Template String
  3. Char, Code Unit, Codepoint
  4. String Escape Sequence
  5. Unicode Escape Sequence

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