hd-utils/lib/utils/string/padStart.js

A handy utils for modern JS developers

/**
* @description function which takes a string of characters and adds a "padding" string of your choice to the start (or left) of the passed string.
 * @example
 *
padStart('foo', 5)
// => "  foo"
 
padStart('foobar', 6)
// => "foobar"
 
padStart(1, 2, '0')
// => "01"
 
padStart(17, 5, 0)
// => "00017"
 */
export default function padStart(input, targetLength, padString = ' ') {
    // Convert input to string
    let str = String(input);
    // If the target length is already met or exceeded, return the original string
    if (str.length >= targetLength) {
        return str;
    }
    // Calculate the number of characters to pad
    const padLength = targetLength - str.length;
    // Ensure the padString is not empty
    if (padString.length === 0) {
        throw new Error('padString cannot be empty');
    }
    // Repeat the padString to create the padding and concatenate it with the original string
    const paddedString = padString
        .repeat(Math.ceil(padLength / padString.length))
        .slice(0, padLength) + str;
    return paddedString;
}