JS中实现Trim()，TrimStart()，TrimEnd() 的方法

//去除字符串头尾空格或指定字符  
String.prototype.Trim = function (c) {
    if (c == null || c == "") {
        var str = this.replace(/^s*/, );
        var rg = /s/;
        var i = str.length;
        while (rg.test(str.charAt(--i)));
        return str.slice(0, i + 1);
    }
    else {
        var rg = new RegExp("^" + c + "*");
        var str = this.replace(rg, );
        rg = new RegExp(c);
        var i = str.length;
        while (rg.test(str.charAt(--i)));
        return str.slice(0, i + 1);
    }
}
//去除字符串头部空格或指定字符  
String.prototype.TrimStart = function (c) {
    if (c == null || c == "") {
        var str = this.replace(/^s*/, );
        return str;
    }
    else {
        var rg = new RegExp("^" + c + "*");
        var str = this.replace(rg, );
        return str;
    }
}

//去除字符串尾部空格或指定字符  
String.prototype.trimEnd = function (c) {
    if (c == null || c == "") {
        var str = this;
        var rg = /s/;
        var i = str.length;
        while (rg.test(str.charAt(--i)));
        return str.slice(0, i + 1);
    }
    else {
        var str = this;
        var rg = new RegExp(c);
        var i = str.length;
        while (rg.test(str.charAt(--i)));
        return str.slice(0, i + 1);
    }
}

调用方法：

var str=,a,b,c,d,;
str=str.TrimStart(",");
//str的值为 a,b,c,d,