Question

我有以下变量：

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

我只想分配定义的值。例如，我可以通过以下方式检查undefined：

undefined

但是如何将其翻译为不分配值？我是否需要事后检查，然后删除属性{{1}}？

Answer 1

如果在帖子数据中未定义属性，你能不能只使用默认值并将它们设置为null？

//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(),
};

如果你真的想剥离它们，这里是你可以使用的基本循环。

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，您可以迭代req.body对象，避免在初始声明后进行验证。

var quote = {};

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

不确定您是否仍想验证req.body对象中的某些值，以便可以添加对它们的检查为null / undefined

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];
   }
}

你甚至可以把它分解成一个很好的可重用函数（下面的基本实现）：

//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;
}

现在您可以在所有路线中使用它。

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

仅在定义时指定属性

1 个答案: