freeCodeCamp/curriculum/challenges/english/02-javascript-algorithms-and-data-structures/object-oriented-programming/understand-own-properties.md

id, title, challengeType, forumTopicId, dashedName

id	title	challengeType	forumTopicId	dashedName
587d7dae367417b2b2512b7b	Understand Own Properties	1	301326	understand-own-properties

--description--

In the following example, the Bird constructor defines two properties: name and numLegs:

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

let duck = new Bird("Donald");
let canary = new Bird("Tweety");

name and numLegs are called own properties, because they are defined directly on the instance object. That means that duck and canary each has its own separate copy of these properties. In fact every instance of Bird will have its own copy of these properties. The following code adds all of the own properties of duck to the array ownProps:

let ownProps = [];

for (let property in duck) {
  if(duck.hasOwnProperty(property)) {
    ownProps.push(property);
  }
}

console.log(ownProps);

The console would display the value ["name", "numLegs"].

--instructions--

Add the own properties of canary to the array ownProps.

--hints--

ownProps should include the values numLegs and name.

assert(ownProps.indexOf('name') !== -1 && ownProps.indexOf('numLegs') !== -1);

You should solve this challenge without using the built in method Object.keys().

assert(!/Object(\.keys|\[(['"`])keys\2\])/.test(code));

You should solve this challenge without hardcoding the ownProps array.

assert(
  !/\[\s*(?:'|")(?:name|numLegs)|(?:push|concat)\(\s*(?:'|")(?:name|numLegs)/.test(
    code
  )
);

--seed--

--seed-contents--

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

let canary = new Bird("Tweety");
let ownProps = [];
// Only change code below this line

--solutions--

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

let canary = new Bird("Tweety");
function getOwnProps (obj) {
  const props = [];

  for (let prop in obj) {
    if (obj.hasOwnProperty(prop)) {
      props.push(prop);
    }
  }

  return props;
}

const ownProps = getOwnProps(canary);