javascript去除前导和后导空格的正则
function trim(input_){ var reg=/(^\s+|\s+$)/gi; return input_.replace(reg, function(march){ return march.replace(/\s+/,""); }); }附replace的实现： var GLOBAL = /(g|gi)$/; var _String_replace = String.prototype.replace; String.prototype.replace = function(expression, replacement) { if (typeof replacement == "function") { // Safari doesn't like functions if (expression && expression.constructor == RegExp) { var regexp = expression; var global = regexp.global; //regexp.global 也不可靠？直接判断正则有没有g吧 if (global == null) global = GLOBAL.test(regexp); // we have to convert global RexpExps for exec() to work consistently //很精巧，即使是g 全局的也要剥离掉 ,使得全局不全局可以很统一和谐的对待 if (global) regexp = new RegExp(regexp.source); // non-global } else { regexp = new RegExp(rescape(expression)); } var match, string = this, result = ""; while (string && (match = regexp.exec(string))) { //匹配项替换后结果以及匹配前缀放入结果 result += string.slice(0, match.index) + replacement.apply(this, match); //这样很好，不用像chrome那样还要记录 previous 的状态，直接把要正则匹配的字符 串截断。 string = string.slice(match.index + match[0].length); //全局不全局只有这一个差别了 if (!global) break; } //最后一次匹配结束位置到字符串结尾 return result + string; } return _String_replace.apply(this, arguments); };