正则表达式 删除string首尾的空白

if (!String.prototype.trim) {
String.prototype.trim = function() {
return this.replace(/^\s+/, "").replace(/\s+$/, "");
};
}

var str = " \t\n test string ".trim();
console.log(str == "test string");//true

String.prototype.trim = function() {
var str = this.replace(/^\s+/, ""),
end = str.length - 1,
ws = /\s/;

while (ws.test(str.charAt(end))) {
end--;
}

return str.slice(0, end + 1);
};

//删除String中的所有空格
String.prototype.trim = function () {
return this.replace(/\s+/g, "");
};