.from() & .of() are not part of the prototype. Creating an array const ages = [13, 15, 21, 32, 35]; and console.log-ing ages.from() or ages.of() would result in a TypeError: ages.from is not a function error.
On Array itself however, Array.from() or Array.of() would be used to convert something that's Array-ish into a legit Array (liiiiiike NodeLists or arguments).
NodeList -> Array:
<div class="kids">
<p>Scrappy</p>
<p>Enigma</p>
<p>Sammy</p>
</div>
<script>
const kids = Array.from(document.querySelectorAll('.kids p'));
console.log(kids);
const names = kids.map(kids => kids.textContent);
console.log(names);
</script>
</body>
</html>
Array.from() can take a 2nd argument, a map function. Instead, of using Array.from() on the doc selector use Array.from(); giving it 2 arguments, the first have the NodeList, the second a function to map over list
const kids = document.querySelectorAll('.kids p');
console.log(kids); // ^NodeList
const names = Array.from(kids, kid => {
console.log(kid); // outputs actual DOM node
return kid.textContent;
});
console.log(names); // array of names
Arguments -> Arrays:
function sumAll() {
// console.log(arguments);
const arr = Array.from(arguments);
return arr.reduce((prev, next) => prev + next, 0);
}
sumAll(2, 4, 6, 8);
Array.of() is pretty straight forward
const ages = Array.of(12, 15, 4);
console.log(ages);
Looking through the proto dropdown you'll see all the usual Array type stuff like .join(), .pop(), .push(), etc.
Array.find() & Array.findIndex()
Common use case is when looking through data that has come from an API, example an array of object items.
.find() will return a true or false. Example: const post = Posts.find(post => post.code === 'whatevercodehere'); will iterate through until it finds specific post, console.log(post); will output found obj containing what you had it look for (if it actually is there, of course).
If you were looking for multiple, .filter() would be output an array of objects, not just one like above.
.findIndex() is when you know what you want, but looking for where in the array it is, position/index-wise. Use case? Position in array to delete item. Example: const post = Posts.findIndex(post => post === 'whatevercodehere') similar to .find() is a true/false type deal. console.loging would output whatever index.
Array.some() & Array.every()
These are not part of ES6, but apparently Wes doesn't feel they get the love they deserve so he's covering them :D
They check the data in an array to check if some of the items meet criteria you're looking for or all items meet what you're looking for.
Array.some():
const ages = [15, 13, 25, 30, 32];
// is there atleast one person over 18/adult
const adultPresent = ages.some(age => age >= 18);
console.log(adultPresent); // outputs true as soon as it hits 25
Array.every():
const ages = [15, 13, 25, 30, 32];
// is everyone old enough to drink
const oldEnoughToDrink = ages.every(age => age >= 21);
console.log(oldEnoughToDrink); // outputs false since there are youngins in the squad