72 lines
2.6 KiB
Markdown
72 lines
2.6 KiB
Markdown
---
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id: 587d7fb9367417b2b2512c12
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title: Chain Search Query Helpers to Narrow Search Results
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challengeType: 2
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forumTopicId: 301533
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---
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## Description
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<section id='description'>
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If you don’t pass the callback as the last argument to `Model.find()` (or to the other search methods), the query is not executed. You can store the query in a variable for later use. This kind of object enables you to build up a query using chaining syntax. The actual db search is executed when you finally chain the method `.exec()`. You always need to pass your callback to this last method. There are many query helpers, here we'll use the most commonly used.
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</section>
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## Instructions
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<section id='instructions'>
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Modify the `queryChain` function to find people who like the food specified by the variable named `foodToSearch`. Sort them by `name`, limit the results to two documents, and hide their age. Chain `.find()`, `.sort()`, `.limit()`, `.select()`, and then `.exec()`. Pass the `done(err, data)` callback to `exec()`.
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### Further Readings
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If you are eager to learn and want to go deeper, You may look at:
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- Indexes ( very important for query efficiency ),
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- Pre/Post hooks,
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- Validation,
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- Schema Virtuals and Model, Static, and Instance methods,
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</section>
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## Tests
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<section id='tests'>
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```yml
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tests:
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- text: Chaining query helpers should succeed
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testString: |
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getUserInput => $.ajax({url: getUserInput('url') + '/_api/query-tools', type: 'POST', contentType:'application/json', data: JSON.stringify([{name: 'Pablo', age: 26, favoriteFoods: ['burrito', 'hot-dog']}, {name: 'Bob', age: 23, favoriteFoods: ['pizza', 'nachos']}, {name: 'Ashley', age: 32, favoriteFoods: ['steak', 'burrito']}, {name: 'Mario', age: 51, favoriteFoods: ['burrito', 'prosciutto']} ]) }).then(data => {
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assert.isArray(data, 'the response should be an Array');
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assert.equal(data.length, 2, 'the data array length is not what expected');
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assert.notProperty(data[0], 'age', 'The returned first item has too many properties');
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assert.equal(data[0].name, 'Ashley', 'The returned first item name is not what expected');
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assert.notProperty(data[1], 'age', 'The returned second item has too many properties');
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assert.equal(data[1].name, 'Mario', 'The returned second item name is not what expected');
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}, xhr => { throw new Error(xhr.responseText); })
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```
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</section>
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## Challenge Seed
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<section id='challengeSeed'>
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</section>
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## Solution
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<section id='solution'>
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```js
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/**
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Backend challenges don't need solutions,
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because they would need to be tested against a full working project.
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Please check our contributing guidelines to learn more.
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*/
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```
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</section>
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