优化小写JSON属性名称的JavaScript代码 [英] Optimizing JavaScript code that lowercases JSON property names

问题描述

我在一个Web应用程序上工作，该应用程序接收带有大写属性名称的JSON数据.我需要这些属性名称为小写，因此我正在使用一个函数来递归遍历JSON对象并将其转换为小写.

I working on a web application that receives JSON data with uppercase property names. I need those property names to be lowercase, so I'm using a function to loop recursively through the JSON object and convert them to lowercase.

问题是我的JSON回复可能很大.我希望该功能执行良好，即使它必须处理具有60,000个属性名称和各种嵌套级别的JSON.

The problem is my JSON replies can get very large. I want the function to perform well even if it has to process JSON with 60,000 property names and various levels of nesting.

小写的功能是:

FN = function (obj)
{var ret = null;
    if (typeof(obj) == "string" || typeof(obj) == "number")
        return obj;
    else if (obj.push)
        ret = [];
    else
        ret = {};
    for (var key in obj)
        ret[String(key).toLowerCase()] = FN(obj[key]);
    return ret;
};

我正在这里进行一些基准测试: http://jsfiddle.net/emw89/7/

And I'm performing some benchmarking here: http://jsfiddle.net/emw89/7/

以上测试在我的计算机上大约在570ms处计时.

The above test clocks in at ~570ms on my machine.

我有什么办法可以改善此功能的性能?

Is there anything I can do to improve the performance of this function?

我关闭了IE，重新打开IE，然后再次运行jsfiddle基准测试-现在对我来说大约是180ms.直到那时我的IE已经连续开放了几天，所以也许这就是造成如此糟糕的性能的原因.无论哪种方式，我仍然对是否有进一步优化此功能的方法感兴趣.任何花费额外时间处理JSON的时间都会直接增加每个AJAX请求的耗时.

I closed my IE, re-opened IE and ran the jsfiddle benchmark again--it's now coming in at ~180ms for me. My IE had been open for a couple days straight until just then, so maybe that's what was causing such poor performance. Either way, I'm still interested if there's a way to optimize this function further. Any time extra time spent processing JSON directly adds to the elapsed time of every AJAX request.

推荐答案

var lowerCache = {};

FN = function (obj)
{
    if (typeof(obj) === "string" || typeof(obj) === "number")
        return obj;

        var l = obj.length;
    if (l) {
        l |= 0;
        var result = [];
        result.length = l;
        for (var i = 0; i < l; i++) {
            var newVal = obj[i];
            result[i] = typeof(newVal) === "string" ? newVal : FN(newVal);
        }
        return result;
    } else {
     var ret = {};
     for (var key in obj) {

         var keyStr = typeof(key) === "string" ? key : String(key);
         var newKey = lowerCache[keyStr];
         if (newKey === undefined) {
             newKey = keyStr.toLowerCase();
             lowerCache[keyStr] = newKey;
         }

         var newVal = obj[key];
         ret[newKey] = typeof(newVal) === "string" ? newVal : FN(newVal);
     }
     return ret;
    }
};

快100％.

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