How JavaScript class properties are accessed

var fish = {
head : 1,
tail : 1,
feature : {
speak : false,
swim : true
}
}

First, the dot operator:

console.log(fish.head);//1
console.log(fish.tail);//1
console.log(fish.feature);//Object { head:1, tail:1, feature: Object}

Second, the [] operator:

console.log(fish['head']);//1

One thing to note here is that the property name must be a string Such as:

console.log(fish[head]);//Error!

So, is the following code correct?

for(var prop in fish) {
console.log(fish[prop]);
}

The answer is yes, this is because the property of the object is traversed in a string type, that is, prop is ‘head’,‘tail’,‘feature’.