将字符串形式保存的正则表达式转为RegExp

str-to-regex.js

var regexStr = rule.regex,
start = regexStr.indexOf('/'),
end = regexStr.lastIndexOf('/'),
source = regexStr.substring(start + 1, end),
flags = regexStr.substring(end + 1, regexStr.length);
if (source.length !== 0) {
    var newRegex = new RegExp(source, flags);
}