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Intersection Observer Example
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| <!DOCTYPE html> | |
| <html lang="ja"> | |
| <head> | |
| <meta charset="UTF-8"> | |
| <script src="dist/main.js"></script> | |
| <style> | |
| .target { | |
| width: 200px; | |
| height: 500px; | |
| margin: 1000px 0; | |
| background-color: gray; | |
| transition: all 1s ease; | |
| } | |
| .hide { | |
| opacity: 0.1; | |
| } | |
| .show { | |
| opacity: 1; | |
| } | |
| </style> | |
| </head> | |
| <body> | |
| <p>IntersectionObserver</p> | |
| <div class="target hide"> | |
| <h2>target</h2> | |
| </div> | |
| </body> | |
| </html> |
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| { | |
| "license": "MIT", | |
| "scripts": { | |
| "dev": "webpack --mode development --module-bundle js=babel-loader --watch", | |
| "build": "webpack --mode production --module-bundle js=babel-loader" | |
| }, | |
| "babel": { | |
| "presets": [ | |
| "@babel/preset-env" | |
| ] | |
| }, | |
| "dependencies": { | |
| "intersection-observer": "^0.5.0" | |
| }, | |
| "devDependencies": { | |
| "@babel/core": "^7.0.0-rc.2", | |
| "@babel/preset-env": "^7.0.0-rc.2", | |
| "babel-loader": "^7.1.5", | |
| "webpack": "^4.17.1", | |
| "webpack-cli": "^3.1.0" | |
| } | |
| } |
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| // import polyfill | |
| import 'intersection-observer' | |
| window.addEventListener('DOMContentLoaded', init, false) | |
| function init () { | |
| const observer = new IntersectionObserver(entries => { | |
| for (const entry of entries) { | |
| check(entry) | |
| } | |
| }) | |
| const targets = document.querySelectorAll('.target') | |
| for (const target of targets) { | |
| observer.observe(target) | |
| } | |
| } | |
| function check (entry) { | |
| if (entry.intersectionRatio > 0) { | |
| console.log('show') | |
| entry.target.classList.add('show') | |
| entry.target.classList.remove('hide') | |
| } else { | |
| console.log('hide') | |
| entry.target.classList.remove('show') | |
| entry.target.classList.add('hide') | |
| } | |
| } |
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