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July 3, 2018 16:12
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ECMAScript map, filter, reduce
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const p = console.log.bind(console); | |
/////////////////////////////////////////////////////////////////////////////// | |
let nums = [3, 12, 21, 27, 44]; | |
let odds = nums.filter(num => num % 2 != 0); | |
p(odds); | |
// → [ 3, 21, 27 ] | |
let evens = nums.filter(num => num % 2 == 0); | |
p(evens); | |
// [ 12, 44 ] | |
//////////////////////////////////////////////////////////////////////////////// | |
// filter urls with a certain characteristic /////////////////////////////////// | |
/* | |
<ul> | |
<li><a href="https://theforce.io">Home page</a></li> | |
<li><a href="http://theforce.io">Home page</a></li> | |
<li><a href="https://theforce.io/about">About</a></li> | |
<li><a href="http://theforce.io/about">About</a></li> | |
</ul> | |
*/ | |
// | |
// querySelectorAll returns a node list, not an array. We need an array | |
// so we can use `filter`. Therefore, we use this little rest parameter | |
// trick so `all_links` is an array. | |
// | |
const all_links = [...document.querySelectorAll('.example-links a')]; | |
// | |
// Let's filter out (exclude) non-https links. | |
// | |
const https_only = all_links.filter(link => /^https:/.test(link.href)); | |
p(https_only.length); | |
// → 2 | |
p(https_only[0].href); | |
// → "https://theforce.io/" | |
p(https_only[1].href); | |
// → "https://theforce.io/about" |
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