javascript - 检查空/空/未定义的更好方法

Question

我想知道是否可以升级我的代码。 我有以下步骤:当找不到标题时，一本书不可用。当一本书的元数据的某些部分未找到时，该书仍然可用，但请求的数据应返回为未知。

var notAvailableMSG = process.env.notAvailableMSG;
var unknownMSG = process.env.unknownMSG;
var bookInfo = [];

// if title is not found = book is not available.
if(bookInfo.title == '' || bookInfo.title == undefined ){
  bookInfo.isbn = isbn;
  bookInfo.title = notAvailableMSG;
  bookInfo.author = notAvailableMSG;
  bookInfo.publisher = notAvailableMSG;
  bookInfo.price = notAvailableMSG;
  bookInfo.currency = notAvailableMSG;
  bookInfo.url = notAvailableMSG;
  bookInfo.releasedate = notAvailableMSG;
  bookInfo.sellable = notAvailableMSG;
}
// Check for other empty values
if(bookInfo.author == '' || bookInfo.author == undefined){
  bookInfo.author = unknownMSG;
}
if(bookInfo.publisher == '' || publisher == undefined){
  bookInfo.publisher = unknownMSG;
}
if(bookInfo.price == '' || bookInfo.price == undefined){
  bookInfo.price = unknownMSG;
}
if(bookInfo.releasedate == '' || bookInfo.releasedate == undefined){
  bookInfo.releasedate = unknownMSG;
}

能否以更好的方式编写这段代码，让这段代码运行得更快(使其更具可读性)？

Answer 1

我认为检查值是否为空的最简单方法是检查它是否为假。它不是最快的代码，但在我看来更容易阅读:

if(!bookInfo.author){
  bookInfo.author = unknownMSG;
}
if(!bookInfo.publisher){
  bookInfo.publisher = unknownMSG;
}
if(!bookInfo.price && bookInfo.price !== 0){
  bookInfo.price = unknownMSG;
}
if(!bookInfo.releasedate){
  bookInfo.releasedate = unknownMSG;
}

您可以查看this发布以查看 JS 中的值何时为假值:

编辑

作为 H.B.说你可以使用一个函数来检查书的每个键。如果你想检查对象的每个键，你也可以使用Object.keys:

['author', 'publisher', 'price', 'releasedate', /* ... */].forEach(key => {
  if (bookInfo[key] === undefined || bookInfo[key] === null || bookInfo[key] === '') {
    bookInfo[key] = unknownMSG;
  }
});