JS: String.prototype.padStart

New in JS2017.

str.padStart(n)

Add spaces in front so the length is n. Return the new string.

"x".padStart(3) === "  x"

str.padStart(n, padstr)

Use padStr to pad.

console.log(
  "x".padStart(3, "0") === "00x",
  "x".padStart(4, "ab") === "abax",
);

/* no padding happens, because "😂" is already length 2 */

console.log("😂".padStart(2, "x") === "😂");

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

Note: "😂".length === 2 〔see JS: String Code Unit〕