请教一个正则表达式的问题

[唐诗三百首]

测试网址: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/match

测试1:

var paragraph = 'p1=222&p3=111';
var regex = '(^|&)p3=([^&]*)(&|$)';
var found = paragraph.match(regex);
console.log(found[2]);

返回: 111 -->正确

测试2:

var paragraph = 'p1=222&[p3]=111';
var regex = '(^|&)[p3]=([^&]*)(&|$)';
var found = paragraph.match(regex);
console.log(found[2]);

返回: Error: Cannot read property '2' of null

测试2因参数名带[], 使得match时误判断了, 请教正确写法.希望返回结果111.

[Logerlink]

[]属于正则的匹配符号，应转义再使用 var regex = '(^|&)\\[p3\\]=([^&]*)(&|$)'

[囧]

var regex = /(^|&)\[p3\]=([^&]*)(&|$)/;