Padding Strings in JavaScript: padLeft & padRight

JS

function padLeft(str, numChars = 4, char = ' ') {
    return (Array.from({ length: numChars }).fill(char).join('') + str).slice(-1 * numChars)
}

padLeft('Max', 8, ' ') // '     Max'
padLeft('1', 4, '0')   // '0001'

JS

function padRight(str, numChars = 4, char = ' ') {
    return (str + Array.from({ length: numChars }).fill(char).join('')).slice(0, numChars)
}

padRight('Max', 8, ' ') // 'Max     '
padRight('1', 4, '0')   // '1000'

JS

function padLeft(str, numChars = 4, char = ' ') {
	// 1. Create an array of `numChars` length (Array.from)
	// 2. Fill it with `char` characters (Array.prototype.fill)
	// 3. Convert it to a string (Array.prototype.join)
	const characters = Array.from({ length: numChars }).fill(char).join('')

	// 4. Concat the characters and the string
	const charsAndString = characters + str

	// 5. Truncate the string from the right so it's at most
	//    `numChars` characters long
	const paddedString = charsAndString.slice(-1 * numChars)

	return paddedString
}