js 处理null、undefined 和空

var Tools = {};

Tools.removeNullOrUndefined = function (obj) {
    //typeof 返回的是字符串，有六种可能："number"、"string"、"boolean"、"object"、"function"、"undefined"  
    if (typeof(obj) == "undefined" || obj == "" || obj == null || obj == "null" || obj.length == 0) {
        return "";
    } else {
        //删除全是空格的情况
        var regu = "^[ ]+$";
        var re = new RegExp(regu);
        if(re.test(obj)){
            return "";
        }else{
            return obj;
        }

    }
}