how to access function/class properties javascript

问题:

This question already has answers here:

Dynamically access object property using variable (15 answers)

Closed 3 years ago.

In the following code, I am having trouble figuring out how to log (in the console) the name and numLegs properties of Penguin (i.e., "emperor" and 2), without changing the inside of the function?

function Penguin(name) {
    this.name = name;
    this.numLegs = 2;
}

var emperor = new Penguin("emperor");

How can I do that?

回答1:

Simply accessing it's properties. Your emperor is an object, which means that you can access properties with . syntax.

function Penguin(name){

   this.name=name;

   this.numLegs=2;

}

var emperor = new Penguin("emperor");

console.log(emperor.name);
console.log(emperor.numLegs);

回答2:

You can use a simple function :

for (var key in emperor) {
  if (emperor.hasOwnProperty(key)) {
    console.log(key + " -> " + emperor[key]);
  }
}

or write

console.log(emperor.numLegs);
console.log(emperor.name);

Reference: How do I loop through or enumerate a JavaScript object?