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40 lines
2.2 KiB
Markdown
40 lines
2.2 KiB
Markdown
<h1>Mastering Change Detection cycle with a scroll example</h1>
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> Author: Thomas Laforge
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### Information
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In this challenge, you will need to optimize the change detection cycles run by Angular.
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Zone.js will trigger a change detection cycle each time a scroll event is dispatched. However we only want to show or hide a button at a specific scroll position. Therefore, we only want to refresh our application once.
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> You can vizualise how many times CD is triggered by installing the [Angular chrome devTool](https://chrome.google.com/webstore/detail/angular-devtools/ienfalfjdbdpebioblfackkekamfmbnh) and starting a new recording on the profiler tab.
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The following video will explain what is the goal of this challenge.
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### Statement
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Your goal for this challenge is to avoid all those unnecessary change detection cycle and trigger a CD only when needed.
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#### Constraint:
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You cannot opt-out of zone.js. If this code is part of a large project and you opt out of zone.js, you will break many things within your application.
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### Submitting your work
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1. Fork the project
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2. clone it
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3. npm install
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4. **nx serve scroll-cd**
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5. _...work on it_
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6. Commit your work
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7. Submit a PR with a title beginning with **Answer:12** that I will review and other dev can review.
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<a href="https://github.com/tomalaforge/angular-challenges/pulls?q=label%3A12+label%3Aanswer"><img src="https://img.shields.io/badge/-Solutions-green" alt="Mastering Change Detection cycle with a scroll example"/></a>
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<!-- TODO: uncomment when done late -->
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<!-- <a href='https://github.com/tomalaforge/angular-challenges/pulls?q=label%3A{challenge number}+label%3A"answer+author"'><img src="https://img.shields.io/badge/-Author solution-important" alt="Mastering Change Detection cycle with a scroll example solution author"/></a>
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<a href="{Blog post url}" target="_blank" rel="noopener noreferrer"><img src="https://img.shields.io/badge/-Blog post explanation-blue" alt="Mastering Change Detection cycle with a scroll example, blog article"/></a> -->
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_You can ask any question on_ <a href="https://twitter.com/laforge_toma" target="_blank" rel="noopener noreferrer"><img src="./../../logo/twitter.svg" height=20px alt="twitter"/></a>
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