Question

如果我有这样的话：

var quiz = [{
    "questionID": "KC2Q4",
    "correctAnswer": "KC2Q4a"
},{
    "questionID": "KC2Q5",
    "correctAnswer": "KC2Q5b" 
}];

并有一个我们可以调用的变量＆＃34;问题＆＃34;具有像KC2Q4这样的字符串值。如何退回＆＃34; correctAnswer＆＃34;对于＆＃34; questionID＆＃34;匹配变量＆＃34;问题＆＃34;在一个新的变量＆＃34;回答＆＃34;？

Answer 1

您应该使用Array.prototype.filter函数（ note filter()是一个ECMA-Script 5.x本机函数：您不需要第三方库或框架!! ）：

var correctAnswer = "KC2Q4a";

// "filter" is like a "where". It iterates each object in your array
// and returns ones that fit the given condition as a closure:
var answersFound = quiz.filter(function(question) {
    return question.correctAnswer == correctAnswer;
});

// You could verify if length > 0, but you want to be sure that
// there's only a single match for a given correct answer, because I feel
// that "correctAnswer" is like an unique id...
if(answersFound.length == 1) {
   // Since there's a found answer to given "correctAnswer",
   // you get the single result (i.e. the question object):
   var answer = answersFound[0];
}

如果您发现上述检查无效（在我的情况下，我称之为防御性编程），您可以通过这种方式直接检索问题对象：

// Without the checking done in the other code listing, you've two risks:
// a. "quiz" could contain no question objects and the filter will return zero results
//    meaning that getting first result array index will throw an error!
//
// b. "quiz" could contain question objects but what you're looking for isn't 
//    present in the so-called array. Error too!
var answer = quiz.filter(function(question) {
    return question.correctAnswer == correctAnswer;
})[0];

Answer 2

你基本上想迭代你的数组，检查每个对象是否有正确的questionID。找到该对象后，返回该对象的correctAnswer属性。

var question = "KC2Q4";
for( var i=0; i<quiz.length; i++ ){
  if( quiz[i].questionID === question ){
    return quiz[i].correctAnswer;
  }
}

javascript访问数组中的对象

2 个答案: