只有定義

Question

分配財產，我有以下變量：

const quote = { 
    author: req.body.author, 
    quote: req.body.quote, 
    source: req.body.source, 
    updatedAt: Date.now(), 
    }; 

我只是想，如果他們被定義爲指定的值。例如，我可以檢查未定義：

if(req.body.author === undefined) { 
    console.log('author undefined'); 
    } 

但是，如何將其轉換爲不分配值？我需要檢查後，如果undefined，然後刪除財產？

Answer 1

難道你不只是使用默認值，並將它們設置爲null，如果屬性未定義在發佈數據？

//Unsure if you want the default value to have any meaning 
//using null would likely achieve what you're asking. 
var default_value = null; 

const quote = { 
    author: req.body.author || default_value, 
    quote: req.body.quote || default_value, 
    source: req.body.source || default_value, 
    updatedAt: Date.now(), 
}; 

如果你真的想剝去它們，這裏有一個你可以使用的基本循環。

for (var i in quote) { 
     if (quote[i] == default_value) { 
      //Unsure how this works with const... might have to change to var 
      delete quote[i]; 
     } 
    } 

或者，您可以遍歷req.body對象，避免在初始聲明之後進行驗證。

var quote = {}; 

for (var i in req.body) { 
    quote[i] = req.body[i]; 
} 

不確定，如果你仍然想驗證對在req.body對象的特定值，所以你可以爲他們被空添加一個檢查/未定義

var quote = {}; 

for (var i in req.body) { 

    //This will only declare the value on the quote object if the value 
    //is not null or undefined. False could be a value you're after so 
    //I avoided using the cleaner version of 'if (!req.body[i]) ...' 
    if (req.body[i] !== null || req.body[i] !== undefined) { 
     quote[i] = req.body[i]; 
    } 
} 

你甚至可以打破伸到一個很好的可重複使用的功能（如下基本實現）：

//Obj would be your post data 
//bad_values would be an array of values you're not interested in. 
function validatePOST (obj, bad_values) { 

    var data = {}; 

    for (var i in obj) { 

     //Check the value isn't in the array of bad values 
     if (bad_values.indexOf(obj[i]) === -1) { 

      data[i] = obj[i]; 
     } 
    } 

    //Return the validated object 
    return data; 
} 

現在，你可以在所有航線使用。

var quote = validatePOST(req.body, [null, undefined]);