Javascript原型覆盖

Question

I have this code that allows me to return a string about the posts connected to a particular post. I tried to use the bracket and dot notation in accessing properties below in the list part ( list=list+this["connectionsTo"[i]].postNum+"\\n"; ) but doesn't work. But then when I used the double dot notation, it worked, why? I believe those two are the same.

function Fencepost(x, y, postNum) {
  this.x = x;
  this.y = y;
  this.postNum = postNum;
  this.connectionsTo = [];
}

Fencepost.prototype = {
  sendRopeTo: function(connectedPost) {
    this.connectionsTo.push(connectedPost);
  },
  removeRope: function(removeTo) {
    var temp = [];
    for (var i = 0; i < this.connectionsTo.length; i++) {
      if (this.connectionsTo[i].postNum != removeTo) {
        temp.push(this.connectionsTo[i]);
      }
    }
    this.connectionsTo = temp;
  },
  movePost: function(x, y) {
    this.x = x;
    this.y = y;
  },
  valueOf: function() {
  return Math.sqrt(this.x * this.x +
                   this.y * this.y);
  }
};

Fencepost.prototype.toString=function(){
var list="";
for(var i=0;i<this.connectionsTo.length;i++){
list=list+this["connectionsTo"[i]].postNum+"\n";
}
  return "Fence post #"+this.postNum+":\nConnected to posts:\n"+list+"Distance from ranch: "+this.valueOf()+" yards";
};

var post10=new Fencepost(3,4,10);
var post11=new Fencepost(5,7,11);
var post12=new Fencepost(6,7,12);
var post13=new Fencepost(8,9,13);
post10.sendRopeTo(post11);
post10.sendRopeTo(post12);
post10.sendRopeTo(post13);
console.log(post10.toString());

Answer 1

Since you are iterating over the this.connectionsTo array, you are looking for

this["connectionsTo"][i]

or the equivalent

this.connectionsTo[i]

instead of

this["connectionsTo"[i]]

which indexes the string, and then takes that character for the property of this .