<script>

//1.正常的方法

String.prototype.trim = function(){

    var str = this;

console.log(str)

    while(str[0] == " "){

        str = str.substr(1);

    }

    while(str[str.length - 1] == " "){

        str = str.substr(0,str.length - 1);

    }

    return str;

}

var str=" ewkeuw rweew 343 ";

str=str.trim();

console.log(str);

//2.正則的方法：

String.prototype.trim1=function(){

    return this.replace(/(^\s*)|(\s*$)/g, "");

}

var str=" ewkeuw rweew 343 ";

str=str.trim1();

console.log(str);

</script>