在Javascript中返回一个字符串

我正在尝试创建一个简单的函数,在调用时将返回正确的字符串：

function getState(abbr){
   if (abbr=="WY")
   {
   return "Wyoming";
   }
}

然后电话是这样的：

var stateName = getState("WY");

然而,所有返回的是：0

对不起,如果我遗漏了明显的东西.

更新 – 我的原始概率是因为“&”这是我正在处理的真实代码：

function getState(abbr){
    var url = "states.asp"
    var state = ""; 
    $.get(url,function(data) {
        var i = 0;
        $.each($('state',data),function(index,el) {            
            if (abbr == ($(this).attr("abbr"))){
                //alert($(this).attr("abbr"));
                state = $(this).text();
            }//if (abbr == $(this).attr("abbr")){
        });//$.each($('state',el) {
    }).success(function() { 
        alert("x" + state);
        return state;
    }); //.success(function() { 
    //$.get(url,function(data) {
    alert("y" + state); 
    return state;
}

我的电话结果是“未定义”：

alert(getState("WY"));

警报(“x”状态)有效.

更新#2 —
这里是states.asp生成的所有内容(现在)…稍后它将返回公司等：

<?xml version="1.0" encoding="utf-8"?>
<STATELIST>
<STATE abbr="AL">Alabama</STATE>
<STATE abbr="AK">Alaska</STATE>
<STATE abbr="AZ">Arizona</STATE>
<STATE abbr="AR">Arkansas</STATE>
<STATE abbr="CA">California</STATE>
<STATE abbr="CO">Colorado</STATE>
<STATE abbr="CT">Connecticut</STATE>
<STATE abbr="DE">Delaware</STATE>
<STATE abbr="FL">Florida</STATE>
<STATE abbr="GA">Georgia</STATE>
<STATE abbr="HI">Hawaii</STATE>
<STATE abbr="ID">Idaho</STATE>
<STATE abbr="IL">Illinois</STATE>
<STATE abbr="IN">Indiana</STATE>
<STATE abbr="IA">Iowa</STATE>
<STATE abbr="KS">Kansas</STATE>
<STATE abbr="KY">Kentucky</STATE>
<STATE abbr="LA">Louisiana</STATE>
<STATE abbr="ME">Maine</STATE>
<STATE abbr="MD">Maryland</STATE>
<STATE abbr="MA">Massachusetts</STATE>
<STATE abbr="MI">Michigan</STATE>
<STATE abbr="MN">Minnesota</STATE>
<STATE abbr="MS">Mississippi</STATE>
<STATE abbr="MO">Missouri</STATE>
<STATE abbr="MT">Montana</STATE>
<STATE abbr="NE">Nebraska</STATE>
<STATE abbr="NV">Nevada</STATE>
<STATE abbr="NH">New Hampshire</STATE>
<STATE abbr="NJ">New Jersey</STATE>
<STATE abbr="NM">New Mexico</STATE>
<STATE abbr="NY">New York</STATE>
<STATE abbr="NC">North Carolina</STATE>
<STATE abbr="ND">North Dakota</STATE>
<STATE abbr="OH">Ohio</STATE>
<STATE abbr="OK">Oklahoma</STATE>
<STATE abbr="OR">Oregon</STATE>
<STATE abbr="PA">Pennsylvania</STATE>
<STATE abbr="RI">Rhode Island</STATE>
<STATE abbr="SC">South Carolina</STATE>
<STATE abbr="SD">South Dakota</STATE>
<STATE abbr="TN">Tennessee</STATE>
<STATE abbr="TX">Texas</STATE>
<STATE abbr="UT">Utah</STATE>
<STATE abbr="VT">Vermont</STATE>
<STATE abbr="VA">Virginia</STATE>
<STATE abbr="WA">Washington</STATE>
<STATE abbr="WV">West Virginia</STATE>
<STATE abbr="WI">Wisconsin</STATE>
<STATE abbr="WY">Wyoming</STATE>
</STATELIST>

解决方法

最简单的方法是制作哈希 – 不需要任何功能.

var states = {
    'AL': 'Alabama','AK': 'Alaska','AZ': 'Arizona','AR': 'Arkansas','CA': 'California','CO': 'Colorado','CT': 'Connecticut',...
    'WY': 'Wyoming'
};

var stateName = states["WY"];

编辑

现在我更好地理解getState()需要从服务器检索状态名称.这使您进入异步编码的世界,这与正常的同步编码完全不同.

要实现的最重要的事情是getState()不能简单地返回给定状态缩写的状态名称.为什么？因为对服务器的ajax调用是异步的 – 换句话说,getState()不会在返回之前等待服务器的响应.

基本上有两种处理异步性的方法：

>将回调函数传递给getState(),告诉它在收到响应时该怎么做
>安排getState()返回一个特殊类型的对象,称为“promise”,可以在调用getState()的地方处理,以便在服务器响应时它会响应.

以下代码采用第二种方法.

var states = {};//cache of state names,with state abbreviations as keys
function getState(abbr) {
    var dfrd = $.Deferred();//A deferred object,whose promise will be returned.
    if(!states[abbr]) {
        $.ajax({
            url: "states.asp",dataType: 'XML',success: function(data) {
                //Load up the cache
                $.each($('state',function(i,el) {
                    states[el.attr('abbr')] = $(el).text();
                });
                //Now resolve or reject the deferred object depending in whether states[abbr] has been cached
                if(states[abbr]) {
                    dfrd.resolve(abbr,states[abbr]);//Success! Let's resolve the deferred object (and its promise).
                }
                else {
                    dfrd.reject(abbr,'States successfully downloaded but ' + abbr + ' was not included');
                }
            },error: function() {
                dfrd.reject(abbr,'Download of states Failed');
            }
        });
    }
    else {
        //The state name is already cached
        //The deferred object (and its promise) can be resolved without needing to make another ajax call.
        dfrd.resolve(abbr,states[abbr]);
    }
    return dfrd.promise();
}

未经测试

现在您需要知道的是如何调用getState().

getState("WY").done(function(abbr,state) {
    alert(abbr + ': ' + state);
    //other stuff here
}).fail(function(abbr,message) {
    alert(abbr + ': ' + message);
    //other stuff here
});

如您所见,您希望getState()返回的值现在显示为.done()函数的第二个参数.为了更好地衡量,缩写(“WY”)显示为第一个参数.

如果你想处理错误条件(总是一个好主意),那么在.fail()回调中这样做.

请参阅代码中的注释,以获取有关一切如何工作的更多线索.

在Javascript中返回一个字符串

解决方法

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