javascript - 在 Javascript 中返回一个字符串

Question

我正在尝试创建一个简单的函数，它会在调用时返回正确的字符串:

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

然后调用是这样的:

var stateName = getState("WY");

但是所有返回的是:0

抱歉，如果我遗漏了一些明显的东西。

更新 - 我的 orig prob 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($('state',data),function(index, el) {
    }).success(function() { 
        alert("x" + state);
        return state;
    }); //.success(function() { 
    //$.get(url, function(data) {
    alert("y" + state); 
    return state;
}

我的电话结果是“undefined”:

alert(getState("WY"));

Alert("x"+ state) 有效。

更新 #2 --- 这是 states.asp 生成的所有内容(目前)...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>

Answer 1

最简单的方法是创建哈希 - 不需要函数。

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。这会将您带入异步编码的世界，这与普通的同步编码截然不同。

要认识到的最重要的事情是 getState() 不能简单地返回给定州缩写的州名。为什么？因为对服务器的 ajax 调用是异步 - 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的方法:

• 将回调函数传递给 getState() 以告诉它在收到响应时做什么
• 安排 getState() 返回一种称为“promise”的特殊类型的对象，可以在调用 getState() 的地方以这样的方式处理它它会在服务器响应时响应。

下面的代码采用了第二种方式。

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', data), 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

现在您只需要知道如何调用 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”)作为第一个参数出现。

如果您想处理错误情况(总是一个好主意)，请在 .fail() 回调中执行此操作。

查看代码中的注释以获取有关一切如何工作的更多线索。