访问对象内键的值

Question

我知道有一些问题与此非常相似，但我似乎无法使任何东西工作。

为简洁起见，我将对此进行总结。我有这个构造函数，它将字符串赋值为键值(赋值)。

var Quote = function() {
  this.quote1 = 'You can discover more about a person in an hour of play than in a year of conversation.';
  this.quote2 = 'Nothing is at last sacred but the integrity of your own mind.';
  this.quote3 = 'We have to fight them daily, like fleas, those many small worries about the morrow, for they sap our energies.';
  this.quote4 = 'Ethics are so annoying. I avoid them on principle.';
  this.quote5 = "Never trust anything that can think for itself if you can't see where it keeps its brain.";
};
module.exports = Quote;

使用AJAX，我将构造函数内部的键值打印到静态页面。然而……我只成功打印了"quote1"、"quote2"等……(只是键的名称)。

访问构造函数的函数是这样的。我的问题是:如何访问构造函数中分配给键的字符串值?这可能吗?

提前谢谢你。

module.exports = function(object) {
  var propArray = Object.keys(object);
  var randomProp = propArray[Math.floor(Math.random() * propArray.length)];
  return {quote: randomProp};
};

Answer 1

在您的函数中，您应该能够使用以下方式访问quote by key:

object[randomProp]

在JavaScript中，可以使用方括号表示法访问对象属性。参见https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Working_with_Objects。

Answer 2

正如您所料，您的代码中有几处错误:)

我已经重写了一遍，并加上了相当详尽的注释。

<script>
// create your 'Quote' class, which can be instantiated as many times as necessary
var Quote = function() {
    this.quote1 = 'You can discover more about a person in an hour of play than in a year of conversation.';
    this.quote2 = 'Nothing is at last sacred but the integrity of your own mind.';
    this.quote3 = 'We have to fight them daily, like fleas, those many small worries about the morrow, for they sap our energies.';
    this.quote4 = 'Ethics are so annoying. I avoid them on principle.';
    this.quote5 = "Never trust anything that can think for itself if you can't see where it keeps its brain.";
};
// now let's set up the 'exports' method on the function's prototype
// this will allow any new instance of the Quote function to call or override this method
// without affecting the master 'Quote' class
Quote.prototype.exports = function() {
    // you don't need to explicitly pass an object to this function
    // just have it reference itself using the 'this' keyword
    var propArray = Object.keys(this);
    var randomProp = propArray[Math.floor(Math.random() * propArray.length)];
    // objects in JavaScript can be handled like associative arrays
    // simply access the key of 'this' with the value provided by 'randomProp'
    return {quote: this[randomProp]};
};
// create a new instance of 'Quote'
// this guy can be used and manipulated independent of the master 'Quote' class
var module = new Quote();
// let's store the value returned by 'exports' in randomQuote
// note the () at the end of module.exports -- this tells JavaScript to treat the object as a function
var randomQuote = module.exports();
// write your quote to the document -- or do whatever else you want to with it at this point
document.write(randomQuote.quote);
</script>

Answer 3

用return object[randomProp]代替return { quote: randomProp }

可以通过点表示法或方括号表示法访问对象属性。

下面是一个来自jsbin的例子https://jsbin.com/yopeli/edit?js,控制台