js string 补全长度

// 尾部补全字符串
let str = "123";
let paddedStr = str.padEnd(5, '0'); // 结果: "12300"

// 头部补全字符串
let str2 = "456";
let paddedStr2 = str2.padStart(5, '0'); // 结果: "00456"

console.log(paddedStr); // 输出: "12300"
console.log(paddedStr2); // 输出: "00456"

function padString(str, targetLength, padChar = ' ', direction = 'end') {
    while (str.length < targetLength) {
        if (direction === 'end') {
            str += padChar;
        } else if (direction === 'start') {
            str = padChar + str;
        }
    }
    return str;
}

let str3 = "789";
let paddedStr3 = padString(str3, 5, '0', 'end'); // 结果: "78900"
console.log(paddedStr3); // 输出: "78900"

let str4 = "abc";
let paddedStr4 = str4.padEnd(6, 'xy'); // 结果: "abcxyx"
console.log(paddedStr4); // 输出: "abcxyx"