dojo/io-query源码解析

　该模块主要对url中的query部分进行处理，我们发送GET请求时，将参数直接放在URL中，经常碰到的需求就是把一个对象转化为query字符串放到url中去发送GET请求。io-query模块便提供了两个方法来处理query：

• objectToQuery将一个object转化成query字符串
• queryToObject将query字符串转化成对象

　　从对象转化成query是拼接的过程，对象的字段和值都需要编码

objectToQuery: function objectToQuery(/*Object*/ map){
        // summary:
        //        takes a name/value mapping object and returns a string representing
        //        a URL-encoded version of that object.
        // example:
        //        this object:
        //
        //    |    {
        //    |        blah: "blah",
        //    |        multi: [
        //    |            "thud",
        //    |            "thonk"
        //    |        ]
        //    |    };
        //
        //        yields the following query string:
        //
        //    |    "blah=blah&multi=thud&multi=thonk"

        var enc = encodeURIComponent, pairs = [];
        for(var name in map){
            var value = map[name];
            // backstop是一个空对象，目的是防止像toString这种继承来的字段被处理
            if(value != backstop[name]){
                var assign = enc(name) + "=";
                if(lang.isArray(value)){
                    //数组的话对每一个数组元素都编码成：multi=thud&multi=thonk
                    for(var i = 0, l = value.length; i < l; ++i){
                        pairs.push(assign + enc(value[i]));
                    }
                }else{
                    pairs.push(assign + enc(value));
                }
            }
        }
        return pairs.join("&"); // String
    }

query到对象是字符串分割的过程，参数和参数值都需要使用decodeURIComponent来解码

queryToObject: function queryToObject(/*String*/ str){
        // summary:
        //        Create an object representing a de-serialized query section of a
        //        URL. Query keys with multiple values are returned in an array.
        //
        // example:
        //        This string:
        //
        //    |        "foo=bar&foo=baz&thinger=%20spaces%20=blah&zonk=blarg&"
        //
        //        results in this object structure:
        //
        //    |        {
        //    |            foo: [ "bar", "baz" ],
        //    |            thinger: " spaces =blah",
        //    |            zonk: "blarg"
        //    |        }
        //
        //        Note that spaces and other urlencoded entities are correctly
        //        handled.

        // 字符串分割
        var dec = decodeURIComponent, qp = str.split("&"), ret = {}, name, val;
        for(var i = 0, l = qp.length, item; i < l; ++i){
            item = qp[i];
            if(item.length){
                var s = item.indexOf("=");
                if(s < 0){// 空值
                    name = dec(item);
                    val = "";
                }else{
                    // 分割"a=b"的形式，name为a，val为b
                    name = dec(item.slice(0, s));
                    val  = dec(item.slice(s + 1));
                }
                //一个name对应多个value则转化为数组
                if(typeof ret[name] == "string"){ // inline'd type check
                    ret[name] = [ret[name]];
                }

                if(lang.isArray(ret[name])){
                    ret[name].push(val);
                }else{
                    ret[name] = val;
                }
            }
        }
        return ret; // Object
    }