Question

非常简单，我如何让我的示波器在这个例子中工作。范围日志的第一个引用到deck功能，但第二个引用到全局窗口。我如何使第二个参考甲板，就像我想要的那样。

谢谢！

function Deck(){
    this.suits = [ // this is an array now
        {
            'suit': 'diamonds',
            'symbol': '&diamondsuit;',
            'color': 'red'
        }

    ]; // close suits

    this.cardValues = [
        {
            'name': 'ace',
            'face': 'A',
            'value': 1
        }
    ]; // close cardValues

    this.cards = [];

    console.log(this);

    this.suits.forEach(function(currentSuit){

        var scope = this;

        console.log(scope);

      // scope doesn't work.
      // obviously, scope references window
      // so how do i get it to refer to the deck like it's supposed to.
      // i looked into using call and apply, and even though the concepts 
      // made sense i couldn't figure it out.
      // fuck this is frustrating!

    });
}

Answer 1

在封闭函数中存储对this的引用，并使用：

var me = this;
this.suits.forEach(function(currentSuit) {
    console.log(me.suits);
});

或使用bind：

this.suits.forEach(function(currentSuit) {
    console.log(this.suits);
}.bind(this));

或者使用forEach的第二个参数:(这可能是最佳解决方案。）

this.suits.forEach(function(currentSuit) {
    console.log(this.suits);
}, this);

Answer 2

你检查过它（？）：

 $this = this;
 this.suits.forEach(function(currentSuit){

    var scope = $this;

    console.log(scope);

});

Answer 3

首先将参考变量保存到卡座范围......

function Deck(){
    var self = this; // save a reference to the deck context

    this.suits = [ // this is an array now
        {
            'suit': 'diamonds',
            'symbol': '&diamondsuit;',
            'color': 'red'
        }

    ]; // close suits

    this.cardValues = [
        {
            'name': 'ace',
            'face': 'A',
            'value': 1
        }
    ]; // close cardValues

    this.cards = [];

    console.log(this);

    this.suits.forEach(function(currentSuit){

        var scope = self;

        console.log(scope);

      // scope doesn't work.
      // obviously, scope references window
      // so how do i get it to refer to the deck like it's supposed to.
      // i looked into using call and apply, and even though the concepts 
      // made sense i couldn't figure it out.
      // fuck this is frustrating!

    });
}

Answer 4

解决此问题的一种方法是将“this”作为第二个参数传递给forEach。所以如果你编辑

   this.suits.forEach(function(currentSuit){
      var scope = this;
        console.log(scope);
    });

到

  this.suits.forEach(function(currentSuit){
      var scope = this;
        console.log(scope);
    }, this);

然后调用new Deck（）将在两种情况下控制日志“Deck”。

我的javascript范围有什么问题

4 个答案: