檢查具有特定屬性值的對象是否存在於一個數組中

Question

我仍然試圖學習CoffeeScript，所以即時通訊只是詢問如何以更簡單的方式編寫此代碼。

for member in draft.members 
     if member.email is emailAddress then throw new Meteor.Error 500, "Cannot add member twice" 

Answer 1

第一步是使它可讀：

for member in draft.members 
    if member.email is emailAddress 
     throw new Meteor.Error 500, 'Cannot add member twice' 

我們可以if -expression使用when消除：

for member in draft.members when member.email is emailAddress 
    throw new Meteor.Error 500, 'Cannot add member twice' 

請不要寫可怕的長隊。請記住if-表達式可以跨越多行。

---

對於一個完整的選擇，你可以，如果你使用Underscore.js或jQuery的消除for -expression。下面是使用Underscore.js（如果你喜歡的jQuery，見$.grep）爲例：

if _.find(draft.members, (m) -> m.email is emailAddress) 
    throw new Meteor.Error 500, 'Cannot add member twice' 

海事組織，for -expression與when是最可讀的。

Answer 2

您還可以使用Array#some，這會導致很簡單的JS，並且不需要外部庫:)

emailAlreadyUsed = draft.members.some (m) -> m.email is emailAddress 
throw new Meteor.Error 500, 'Cannot add member twice' if emailAlreadyUsed