Javascript - 多個複雜if語句

Question

Im在javaScript中使用多個複雜語句掙扎着，想知道是否有人可以指引我朝着正確的方向。

function findFlights() 
    { 
    var yourDestination = readTheDestination(); 
    var yourAirline = readTheAirline(); 
    var yourFare = readTheFare(); 


    if (yourDestination == 'Choose your destination') 
     { 
     displayMessage('<B>Please choose a destination city from the Destination menu and then click Find flights again.</B>'); 
     } 
    else 
     { 
     var destinationTime, destinationOperator, destinationFare; 
     var message = '<B>You asked about flights to ' + yourDestination + '</B><BR>' + ""; 

     for (var i=0; i < flightTimes.length; i++)      //flight destinations 
     { 
     if // statement            // IF flight: 
      ((flightDestinations[i] == yourDestination &&    // destination = selected destination & 
      yourAirline == 'Any airline' &&        // airline = any airline & 
      yourFare == 'Any price'))         // fare <= chosen fare 
      ||               // OR 
      (flightDestinations[i] == yourDestination &&    // destination = selected destination & 
      yourAirline == flightOperators[i] &&      // airline = chosen airline & 
      yourFare <= flightFares[i]))        // fare <= chosen fare 

      { 
      destinationTime = flightTimes[i]; 
      destinationOperator = flightOperators[i]; 
      destinationFare = flightFares[i]; 



      message += destinationTime + ' ' + destinationOperator + '. £' + destinationFare + '<BR>'; 
      displayMessage(message); 

      } 
     } 
     else if (flightDestinations[i] == yourDestination && 
       flightOperators[i] != yourAirline && 
       flightFares[i] != yourFare) 
      { 
      displayMessage('There are no flights to ' + yourDestination + ' with ' + yourAirline + '. Please select Any Airline and try again.'); 
      } 
     } 

這是我到目前爲止，它使我灰色。

Answer 1

我不確定問題是什麼，但您應該使用更一致的縮進，複雜的if語句一定會變得更清晰。

我的規則：

• 使用標籤來根據範圍縮進行代碼（例如+1片而花括號，if報表內等）
• 不使用標籤爲別的;使用空間進行調準，多個空格（如有必要的話，使用空格排隊在if聲明你的條件，如果該語句跨越多行）

Answer 2

雖然我認爲這不是一個必要的調整，你可以寫代碼如下：

if (yourDestination == 'Choose your destination') { 
    displayMessage('<B>Please choose a destination city from the Destination menu and then click Find flights again.</B>'); 
    return; 
} 

這可以幫助你去除else及其支架{...}。

您可以更改爲環，以減少代碼大小：

if(flightDestinations[i] != yourDestination) continue; 

這樣，你不需要反覆寫這個條件。

Answer 3

你在這裏不匹配您的括號：

((flightDestinations[i] == yourDestination &&    // destination = selected destination & 
yourAirline == 'Any airline' &&        // airline = any airline & 
yourFare == 'Any price'))         // fare <= chosen fare 
||               // OR 
(flightDestinations[i] == yourDestination &&    // destination = selected destination & 
yourAirline == flightOperators[i] &&      // airline = chosen airline & 
yourFare <= flightFares[i]))        // fare <= chosen fare 

變化yourFare == 'Any price'))到yourFare == 'Any price')。

Answer 4

重構複雜的代碼的功能

如果你有複雜的if語句嘗試和功能包起來。所以

(flightDestinations[i] == yourDestination && 
yourAirline == 'Any airline' && 
yourFare == 'Any price') 

可能成爲

function YourDestinationIsTheSameForAnyAirlineOrPrice(flightDestination, yourDestination, yourAirline, yourFare){ 
    return flightDestination == yourDestination && 
     yourAirline == 'Any airline' && 
     yourFare == 'Any price'; 
} 

// And called from if 
if (YourDestinationIsTheSameForAnyAirlineOrPrice(flightDestinations[i], yourDestination, yourAirline, yourFare)) {} 

而不是試圖破譯你有一個函數的名字，告訴你它做什麼的if語句。

使用在多個陣列

具體到你的例子，我也想嘗試，並創建包含目標，時間和航空公司一個航班對象的對象。例如：

var flight = { 
    destination = "London", 
    operator = "BA", 
    time = "18:00 UTC", 
    fare = "£239829" 
} 

這應該使代碼比使用多個數組更可讀。例如：

destinationTime = flightTimes[i]; 
destinationOperator = flightOperators[i]; 
destinationFare = flightFares[i]; 

message += destinationTime + ' ' + destinationOperator + '. £' + destinationFare + '<BR>'; 

// Using an object 
message += flight.Time + ' ' + flight.Operator + '. £' + flight.Fare + '<br />'; 

返回早期

最後，我想盡快擺脫功能。如此使用：

if (yourDestination == 'Choose your destination') { 
    displayMessage('<B>Please choose a destination city from the Destination menu and then click Find flights again.</B>'); 
    return; 
} 

而不是if ... else。我個人覺得這更具可讀性，所以請隨時忽略這一點。