js 去字符串两边空格

String.prototype.trim = function () {
    return this.replace(/(^\s*)|(\s*$)/g, "");
}
String.prototype.ltrim = function () {
    return this.replace(/(^\s*)/g, "");
}
String.prototype.rtrim = function () {
    return this.replace(/(\s*$)/g, "");
}