Created
December 24, 2019 21:10
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| // Long Polling | |
| let ID = 1 | |
| const foo = document.createElement('p') | |
| async function timeout (callback, delay) { | |
| return await setTimeout(callback, delay) | |
| } | |
| function polling () { | |
| return timeout(() => { | |
| const xhr = new XMLHttpRequest(), | |
| method = 'GET', | |
| url = `https://jsonplaceholder.typicode.com/todos/${ID}` | |
| xhr.open(method, url, true) | |
| xhr.onreadystatechange = () => { | |
| if (xhr.readyState === 4 && xhr.status === 200) { | |
| console.log('responseText:', xhr.responseText) | |
| } | |
| } | |
| xhr.onloadstart = () => console.log('Download started', new Date().getTime()) | |
| xhr.onload = e => { | |
| const result = JSON.parse(e.target.response) | |
| foo.innerText = result.title | |
| result.completed && (foo.style.textDecoration = 'line-through') | |
| document.body.prepend(foo) | |
| ID++ | |
| polling() | |
| } | |
| xhr.onprogress = event => console.log('progress:' ,{ | |
| loaded: event.loaded, | |
| total: event.total | |
| }) | |
| xhr.onloadend = () => console.log('Download end', new Date().getTime()) | |
| xhr.onabort = () => console.warn('The request was aborted') | |
| // xhr.abort() | |
| xhr.ontimeout = () => console.error('Timeout!!') | |
| xhr.onerror = event => console.error('Error:', event) | |
| xhr.send() | |
| }, 3000) | |
| } | |
| window.addEventListener('online', () => { | |
| polling() | |
| console.log('connection online!') | |
| }) | |
| window.addEventListener('offline', () => { | |
| polling() | |
| console.log('connection offline!') | |
| }) | |
| polling() | |
| // or alternative: https://github.com/fanout/pollymer | |
| // Server-Sent Events | |
| // https://github.com/EventSource/eventsource |
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