String.prototype.padStart()
String.prototype.padStart() is a JavaScript method in the String category. Pads the string from the start. The syntax is str.padStart(targetLength, padString). A typical example: "5".padStart(3, "0") // "005". Another practical use — Zero-pad numbers: const hours = 9, minutes = 5 const time = String(hours).padStart(2, '0') + ':' + String(minutes).padStart(2, '0') console.log(time) // '09:05' Its time complexity is O(n), which matters when it runs over large inputs. A close sibling is String.prototype.charAt(), which returns the character at the specified index. A close sibling is String.prototype.charCodeAt(), which returns the Unicode value of the character at the specified index. A close sibling is String.prototype.concat(), which concatenates strings together. A close sibling is String.prototype.includes(), which checks if a string contains a specified substring. More about this category: String methods for text manipulation — split, replace, trim, match, and more. Related String methods: String.prototype.charAt(), String.prototype.charCodeAt(), String.prototype.concat(), String.prototype.includes(), String.prototype.indexOf(), String.prototype.lastIndexOf(), String.prototype.match(), String.prototype.matchAll().