正则表达式匹配的字符要同时存在"()",才能返回true

Question

var re = /$?[0-9]{3}$?/

var str1 = '789';
console.log(re.test(str1));//返回true
var str2 = '(789)';
console.log(re.test(str2)); //&nb

三叔 · Answer

var re = /($[0-9]{3}(?=$))|(^[0-9]{3}$)/g;

console.log(re.test("789"));
console.log(re.test("(789"));
console.log(re.test("789)"));
console.log(re.test("(789)"));

欧阳克 · Answer

var re = /$\d{3}$|^(?!$)\d{3}(?!$)/

先匹配'(789)'情况，在匹配'789'

三叔 · Answer

var re = /[0-9]{3}|(([0-9]{3}))/