76 lines
1.8 KiB
Markdown
76 lines
1.8 KiB
Markdown
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---
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id: 587d7dae367417b2b2512b7a
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title: Verify an Object's Constructor with instanceof
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challengeType: 1
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forumTopicId: 301337
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dashedName: verify-an-objects-constructor-with-instanceof
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---
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# --description--
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Anytime a constructor function creates a new object, that object is said to be an <dfn>instance</dfn> of its constructor. JavaScript gives a convenient way to verify this with the `instanceof` operator. `instanceof` allows you to compare an object to a constructor, returning `true` or `false` based on whether or not that object was created with the constructor. Here's an example:
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```js
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let Bird = function(name, color) {
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this.name = name;
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this.color = color;
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this.numLegs = 2;
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}
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let crow = new Bird("Alexis", "black");
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crow instanceof Bird; // => true
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```
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If an object is created without using a constructor, `instanceof` will verify that it is not an instance of that constructor:
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```js
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let canary = {
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name: "Mildred",
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color: "Yellow",
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numLegs: 2
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};
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canary instanceof Bird; // => false
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```
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# --instructions--
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Create a new instance of the `House` constructor, calling it `myHouse` and passing a number of bedrooms. Then, use `instanceof` to verify that it is an instance of `House`.
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# --hints--
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`myHouse` should have a `numBedrooms` attribute set to a number.
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```js
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assert(typeof myHouse.numBedrooms === 'number');
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```
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You should verify that `myHouse` is an instance of `House` using the `instanceof` operator.
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```js
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assert(/myHouse\s*instanceof\s*House/.test(code));
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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 House(numBedrooms) {
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this.numBedrooms = numBedrooms;
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}
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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 House(numBedrooms) {
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this.numBedrooms = numBedrooms;
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}
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const myHouse = new House(4);
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console.log(myHouse instanceof House);
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```
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