函数返回一个对象

我正在 codecademy.com 上一些 JavaScript/jQuery 课程。正常情况下，课程会提供答案或提示，但是对于这一个，它没有提供任何帮助，我有点困惑的说明。

它说让函数 make GamePlayer 返回一个有三个键的对象。

//First, the object creator
function makeGamePlayer(name,totalScore,gamesPlayed) {
//should return an object with three keys:
// name
// totalScore
// gamesPlayed
}

我不确定我是否该这么做

//First, the object creator
function makeGamePlayer(name,totalScore,gamesPlayed) {
//should return an object with three keys:
// name
// totalScore
// gamesPlayed


this.name =  name;
this.totalScore = totalScore;
this.gamesPlayed = gamesPlayed;
}

或者类似的东西

 //First, the object creator
function makeGamePlayer(name,totalScore,gamesPlayed) {
//should return an object with three keys:
// name
// totalScore
// gamesPlayed


var obj = {
this.name =  name;
this.totalScore = totalScore;
this.gamesPlayed = gamesPlayed;
}
}

我必须能够修改对象的属性后，其创建。

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小开

You can simply do it like this with an object literal:

function makeGamePlayer(name,totalScore,gamesPlayed) {
return {
name: name,
totalscore: totalScore,
gamesPlayed: gamesPlayed
};
}
小开
最佳答案

In JavaScript, most functions are both callable and instantiable: they have both a [[Call]] and [[Construct]] internal methods.

As callable objects, you can use parentheses to call them, optionally passing some arguments. As a result of the call, the function can return a value.

var player = makeGamePlayer("John Smith", 15, 3);

The code above calls function makeGamePlayer and stores the returned value in the variable player. In this case, you may want to define the function like this:

function makeGamePlayer(name, totalScore, gamesPlayed) {
// Define desired object
var obj = {
name:  name,
totalScore: totalScore,
gamesPlayed: gamesPlayed
};
// Return it
return obj;
}

Additionally, when you call a function you are also passing an additional argument under the hood, which determines the value of this inside the function. In the case above, since makeGamePlayer is not called as a method, the this value will be the global object in sloppy mode, or undefined in strict mode.

As constructors, you can use the new operator to instantiate them. This operator uses the [[Construct]] internal method (only available in constructors), which does something like this:

  1. Creates a new object which inherits from the .prototype of the constructor
  2. Calls the constructor passing this object as the this value
  3. It returns the value returned by the constructor if it's an object, or the object created at step 1 otherwise.
var player = new GamePlayer("John Smith", 15, 3);

The code above creates an instance of GamePlayer and stores the returned value in the variable player. In this case, you may want to define the function like this:

function GamePlayer(name,totalScore,gamesPlayed) {
// `this` is the instance which is currently being created
this.name =  name;
this.totalScore = totalScore;
this.gamesPlayed = gamesPlayed;
// No need to return, but you can use `return this;` if you want
}

By convention, constructor names begin with an uppercase letter.

The advantage of using constructors is that the instances inherit from GamePlayer.prototype. Then, you can define properties there and make them available in all instances

小开

I would take those directions to mean:

  function makeGamePlayer(name,totalScore,gamesPlayed) {
//should return an object with three keys:
// name
// totalScore
// gamesPlayed


var obj = {  //note you don't use = in an object definition
"name": name,
"totalScore": totalScore,
"gamesPlayed": gamesPlayed
}
return obj;
}
小开

Both styles, with a touch of tweaking, would work.

The first method uses a Javascript Constructor, which like most things has pros and cons.

 // By convention, constructors start with an upper case letter
function MakePerson(name,age) {
// The magic variable 'this' is set by the Javascript engine and points to a newly created object that is ours.
this.name = name;
this.age = age;
this.occupation = "Hobo";
}
var jeremy = new MakePerson("Jeremy", 800);

On the other hand, your other method is called the 'Revealing Closure Pattern' if I recall correctly.

function makePerson(name2, age2) {
var name = name2;
var age = age2;


return {
name: name,
age: age
};
}
小开

The latest way to do this with ES2016 JavaScript

let makeGamePlayer = (name, totalScore, gamesPlayed) => ({
name,
totalScore,
gamesPlayed
})

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