103 lines
2.0 KiB
Markdown
103 lines
2.0 KiB
Markdown
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---
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id: 587d7dae367417b2b2512b7b
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title: Understand Own Properties
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challengeType: 1
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forumTopicId: 301326
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dashedName: understand-own-properties
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---
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# --description--
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In the following example, the `Bird` constructor defines two properties: `name` and `numLegs`:
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```js
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function Bird(name) {
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this.name = name;
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this.numLegs = 2;
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}
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let duck = new Bird("Donald");
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let canary = new Bird("Tweety");
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```
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`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`:
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```js
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let ownProps = [];
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for (let property in duck) {
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if(duck.hasOwnProperty(property)) {
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ownProps.push(property);
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}
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}
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console.log(ownProps); // prints [ "name", "numLegs" ]
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```
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# --instructions--
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Add the `own` properties of `canary` to the array `ownProps`.
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# --hints--
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`ownProps` should include the values `"numLegs"` and `"name"`.
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```js
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assert(ownProps.indexOf('name') !== -1 && ownProps.indexOf('numLegs') !== -1);
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```
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You should solve this challenge without using the built in method `Object.keys()`.
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```js
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assert(!/Object(\.keys|\[(['"`])keys\2\])/.test(code));
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```
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You should solve this challenge without hardcoding the `ownProps` array.
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```js
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assert(
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!/\[\s*(?:'|")(?:name|numLegs)|(?:push|concat)\(\s*(?:'|")(?:name|numLegs)/.test(
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code
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)
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);
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```
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# --seed--
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## --seed-contents--
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```js
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function Bird(name) {
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this.name = name;
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this.numLegs = 2;
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}
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let canary = new Bird("Tweety");
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let ownProps = [];
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// Only change code below this line
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```
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# --solutions--
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```js
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function Bird(name) {
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this.name = name;
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this.numLegs = 2;
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}
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let canary = new Bird("Tweety");
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function getOwnProps (obj) {
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const props = [];
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for (let prop in obj) {
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if (obj.hasOwnProperty(prop)) {
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props.push(prop);
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}
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}
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return props;
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}
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const ownProps = getOwnProps(canary);
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```
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