trim():清空左右兩邊空白

const greeting = '   Hello world!   ';
const greetingTrim=greeting.trim();
console.log(greetingTrim);
//Hello world!"

trimEnd():清空結束空白

const greetTrimEnd=greeting.trimEnd();
console.log('清除結束的空白',greetTrimEnd)
//"清除結束的空白" "   Hello world!"

trimStart():清空開始空白

greenTrimStart=greeting.trimStart();;

console.log(‘清除開始的空白’,greenTrimStart)
//“清除開始的空白” “Hello world!   “