下拉選擇值並不成爲真正的價值，並在JavaScript中工作

Question

我有一個語言下拉菜單，我嘗試提醒用戶必須先選擇一種語言，然後再進一步處理，如languageOption可以變成字符串並進入數組。但它不工作，我不明白爲什麼。我試過了：

alert("You didn't choose any language."); 
    console.alert("You didn't choose any language."); 
    console.log("You didn't choose any language."); 

但他們都不起作用。

而且我認爲另一種方式來解決這個問題，這是我做

<option value="1" selected>English (American)</option> 

但隨後的值=「1」不會成爲變量「languageOption」的一個值。所以當我在控制檯中看到時，陣列不響應，也不知道該怎麼做。我不明白爲什麼數組沒有響應。

任何幫助，我將不勝感激。 下面是我的代碼：

<select id="languageSelection" style=display:none> 
     <option value="">Choose a language</option> 
     <option value="1">English (American)</option> 
     <option value="2">Chinese (Mandarin)</option> 
     <option value="3">Japanese</option> 
</select> 

    var audioSrc = "sound/" 
    var audioType = ".wav"; 

    // default number of random question, if user this used the dropdown 
    var default_numFollowUp = 4; 
    // default delai (seconds) between random questions, if user this used the dropdown 
    var default_secFollowUp = 10; 

    // Create the audio element 
    var audioElement = document.createElement('audio'); 

    var endingArr = []; 
    var runThroughArr = []; 
    var randomArr = []; 

    var languageOption = parseInt($("#languageSelection").val()); 

    $("#languageSelection").on("change", function(){ 

     languageOption = $(this).val(); // Make languageOption value be string 

     //if(languageOption.length==0){languageOption=1;} 

     console.log("langugeOption is " + languageOption); 

     console.log("Language changed to: "+ $(this).find("option").eq($(this)[0].selectedIndex).text() + " (Index: "+languageOption+")"); 

     console.log(typeof(languageOption)); // Outputs string 

     endingArr = []; 
     runThroughArr = []; 
     randomArr = []; 

     if(languageOption === ""){ 
      alert("You didn't choose any language."); 
      console.alert("You didn't choose any language."); 
      console.log("You didn't choose any language."); 
     } 
     else if(languageOption === "1"){ 
      console.log("English"); 
      for(i = 0; i < intro_playList.length; i++){ 
       if(intro_playList[i].stage === "ending"){ endingArr.push(i); } 
       if(intro_playList[i].runThrough){ runThroughArr.push(i); } 
       if(intro_playList[i].random){ randomArr.push(i); } 
      } 
     } 
     else if (languageOption === "2"){ 
      console.log("Chinese"); 
      for(i = 0; i < intro_playList_chi.length; i++){ 
       if(intro_playList_chi[i].stage === "ending"){ endingArr.push(i); } 
       if(intro_playList_chi[i].runThrough){ runThroughArr.push(i); } 
       if(intro_playList_chi[i].random){ randomArr.push(i); } 
      } 
     } 
    }); 

Answer 1

您需要加載文檔後分配平變化的功能。使用jQuery，你可以這樣做

var languageOption; 
$(document).on("ready", function() { 
    languageOption = $("#languageSelection").val(); 
    $("#languageSelection").on("change", function() { 
     your code here ... 
    } 
}