使用JavaScript将项添加到数组中的每个对象

Question

我正在制作一种琐碎的追求游戏。 我有成千上万的问题和答案; 见下面的例子：

var trivialPursuitCards = [
   {
    question: "What nationality was Chopin?",
    answer: ["American", "Polish", "German", "Czech"],
    difficulty: 2
   }, 
   {
    question: "Who cut Van Gogh's ear?",
    answer: ["His sister", "His brother", "Himself", "He was born that way"],
    difficulty: 2
   }
];

现在我只需要为每张卡添加一个属性，即： rightAnswer: undefined 。

为所有卡片完成这项工作的最佳方法是什么？

Answer 1

for(var i=0; i<trivialPursuitCards.length; i++) {
    trivialPursuitCards[i].rightAnswer = undefined;
}

https://jsfiddle.net/o0pa4z0w/

Answer 2

使用map然后添加你的财产： -

 var trivialPursuitCards = [{ question: "What nationality was Chopin?", answer: ["American", "Polish", "German", "Czech"], difficulty: 2 }, { question: "Who cut Van Gogh's ear?", answer: ["His sister", "His brother", "Himself", "He was born that way"], difficulty: 2 }]; var update = trivialPursuitCards.map(function(e, i) { e.rightAnswer = undefined; return e; }); console.log(update); 

Answer 3

trivialPursuitCards.map(function (card) { card.rightAnswer = null; });

因为添加null不是undefined更好，因为rightAnswer应该存在，但是当前没有设置。

Answer 4

正如Juhana所指出的那样：

默认情况下，不存在未定义的属性，因此您似乎不太可能需要明确设置它。

但是，如果您真的想这样做，可以使用Array.prototype.map() ：

trivialPursuitCards = trivialPursuitCards.map(element=>
  element.rightAnswer = undefined
)