javascript - 如何在 JavaScript 中将输入括号与正则表达式匹配？

Question

我不知道如何将输入括号与 JavaScript 匹配。

输入字符串示例:

(pen)
((pen) and orange)

如果输入字符串如下所示，它应该返回 false:

(pen
pen)
(pen) and orange)
((pen and orange )
((pen) and orange 
)(pen and orange )(
(pen and )orange() 

Answer 1

正则表达式会很困惑。使用简单的计数器更容易完成。

function parenthesesBalanced(string) {
    var count = 0;

    for (var i = 0, l = string.length; i < l; i++) {
        var char = string.charAt(i);

        if (char == "(") {
            // Opening parenthesis is always OK
            count++;
        } else if (char == ")") {
            // If we're at the outer level already it's not valid
            if (count == 0) return false;
            count--;
        }
    }

    return (count == 0);
}