我看到了这个代码示例:
function Dog(name) {
this.name = name;
EventEmitter.call(this);
}
它“继承”自EventEmitter,但是call()方法到底做了什么呢?
发布于 2013-02-23 20:57:06
基本上,Dog
应该是一个具有name
属性的构造函数。在创建Dog
实例期间执行EventEmitter.call(this)
时,它会将从EventEmitter
构造函数声明的属性追加到Dog
。
请记住:构造函数仍然是函数,并且仍然可以用作函数。
//An example EventEmitter
function EventEmitter(){
//for example, if EventEmitter had these properties
//when EventEmitter.call(this) is executed in the Dog constructor
//it basically passes the new instance of Dog into this function as "this"
//where here, it appends properties to it
this.foo = 'foo';
this.bar = 'bar';
}
//And your constructor Dog
function Dog(name) {
this.name = name;
//during instance creation, this line calls the EventEmitter function
//and passes "this" from this scope, which is your new instance of Dog
//as "this" in the EventEmitter constructor
EventEmitter.call(this);
}
//create Dog
var newDog = new Dog('furball');
//the name, from the Dog constructor
newDog.name; //furball
//foo and bar, which were appended to the instance by calling EventEmitter.call(this)
newDog.foo; //foo
newDoc.bar; //bar
发布于 2015-12-23 03:56:22
EventEmitter.call(this);
这一行大致相当于在具有经典继承的语言中调用super()。
https://stackoverflow.com/questions/15040717
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