將AJAX GET響應的一部分（以JSON形式）存儲到字符串變量中的問題

Question

我試圖通過AJAX將GET請求的一部分結果存儲到字符串變量中時出現問題。

基本上，我想使它包含GET請求操作的某個函數將返回該操作的結果。

var count = 0; 

$.getJSON("https://api.icndb.com/jokes/count", function(data){ 
    count = data.value+1; 
    for (i = 1; i < count; i++){ 
     if (i != 1) { 
      setTimeout(jokeGet, i*7500, i); 
     } 
     else { 
      jokeGet(i); 
     } 
    } 
}); 

function jokeGet(n) { 
    var str = ""; 
    $.getJSON("https://api.icndb.com/jokes/" + n, function(data){ 
     if (data.type != "NoSuchQuoteException") { 
      $(".joke").html(data.value.joke); 
      str = data.value.joke; 
     } 
     else { 
      count++; 
     } 
    }); 

    return str; 
} 

API我正在發出請求以將信息存儲在JSON樹中。下面是這種樹的兩個例子：

{ "type": "success", "value": { "id": 1, "joke": "Chuck Norris uses ribbed condoms inside out, so he gets the pleasure.", "categories": ["explicit"] } } 

{ "type": "NoSuchQuoteException", "value": "No quote with id=8." } 

但是，每當我運行單元測試（通過QUnit），事實證明，在任何及所有情況下，jokeGet()函數返回一個空字符串。這是我覺得很奇怪的事情，因爲我認爲str = data.value.joke系列會讓它變成這樣，這個笑話被存儲在變量str中。

顯然，因爲str總是以空字符串的形式返回，所以情況並非如此。有什麼建議，爲什麼這是？

更新

考慮到的是什麼，我現在在做的目的不是爲了讓程序工作，但做單元測試，以證明程序工作，我已決定將「單元測試」文件：

QUnit.test("cn_jokes", function(assert) { 
    function joke(n, expected) { 
     assert.equal(jokeGet(n), expected); 
    } 
    joke(1, "Chuck Norris uses ribbed condoms inside out, so he gets the pleasure."); 
    joke(8, undefined); 
    joke(163, "Ninjas want to grow up to be just like Chuck Norris. But usually they grow up just to be killed by Chuck Norris."); 
    joke(221, "Chuck Norris is the only person to ever win a staring contest against Ray Charles and Stevie Wonder."); 
    joke(352, "Chuck Norris doesn't see dead people. He makes people dead."); 
    joke(502, "Chuck Norris insists on strongly-typed programming languages."); 
    joke(526, "No one has ever pair-programmed with Chuck Norris and lived to tell about it."); 
    joke(598, "Once Chuck Norris and Superman had a competition. The loser had to wear his underwear over his pants."); 
}); 

正如你可以看到，我想獲得的jokeGet()功能，具體，返回笑話值。請讓我知道這是否可能。

Answer 1

$.getJSON是異步的前返回值;您的代碼將在請求發出時繼續運行。正因爲如此，str很久之前通過您傳遞給getJSON運行的回調返回。你或許應該有jokeGet需要一個回調函數，並調用它的請求完成（通過data.value.joke作爲參數）時：

function jokeGet(n, callback) { 
    $.getJSON("https://api.icndb.com/jokes/" + n, function(data){ 
     if (data.type != "NoSuchQuoteException") { 
      $(".joke").html(data.value.joke); 
      if (callback !== undefined && callback !== null) 
       callback(data.value.joke); 
     } 
     else { 
      count++; 
      if (callback !== undefined && callback !== null) 
       callback(undefined); // not sure if you want undefined or "" in this case 
     } 
    }); 
} 

編輯：您可以使用異步回調與QUnit。如上所述，只需使用assert.async()here：

QUnit.test("cn_jokes", function(assert) { 
    var done = assert.async(); 
    var jokesDone = 0; 
    var numJokes = 8; // make sure to change this if you add more 
    function joke(n, expected) { 
     jokeGet(n, function(j) { 
      assert.equal(j, expected); 
      if (++jokesDone == numJokes) done(); 
     } 
    } 
    joke(1, "Chuck Norris uses ribbed condoms inside out, so he gets the pleasure."); 
    joke(8, undefined); 
    joke(163, "Ninjas want to grow up to be just like Chuck Norris. But usually they grow up just to be killed by Chuck Norris."); 
    joke(221, "Chuck Norris is the only person to ever win a staring contest against Ray Charles and Stevie Wonder."); 
    joke(352, "Chuck Norris doesn't see dead people. He makes people dead."); 
    joke(502, "Chuck Norris insists on strongly-typed programming languages."); 
    joke(526, "No one has ever pair-programmed with Chuck Norris and lived to tell about it."); 
    joke(598, "Once Chuck Norris and Superman had a competition. The loser had to wear his underwear over his pants."); 
}); 

Answer 2

嘗試使用裏面的return語句，如果塊

if(condition){ 
return str; 
} else { 
return 
} 

我想這品行是由於JS的異步性質，GET請求完成