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๐Ÿ“ฐCheat Sheet

Cheat sheet: JavaScript Array methods

Deriving a new Array from an existing Array:

['โ– ','โ—','โ–ฒ'].slice(1, 3)          โŸผ ['โ—','โ–ฒ']
['โ– ','โ—','โ– '].filter(x => x==='โ– ') โŸผ ['โ– ','โ– ']
    ['โ–ฒ','โ—'].map(x => x+x)        โŸผ ['โ–ฒโ–ฒ','โ—โ—']
    ['โ–ฒ','โ—'].flatMap(x => [x,x])  โŸผ ['โ–ฒ','โ–ฒ','โ—','โ—']

Computing a summary of an Array:

['โ– ','โ—','โ–ฒ'].some(x => x==='โ—')  โŸผ true
['โ– ','โ—','โ–ฒ'].every(x => x==='โ—') โŸผ false

['โ– ','โ—','โ–ฒ'].join('-') โŸผ 'โ– -โ—-โ–ฒ'

['โ– ','โ—'].reduce((result,x) => result+x, 'โ–ฒ')      โŸผ 'โ–ฒโ– โ—'
['โ– ','โ—'].reduceRight((result,x) => result+x, 'โ–ฒ') โŸผ 'โ–ฒโ—โ– '

Changing all of an Array (the input Array is modified and returned):

['โ– ','โ—','โ–ฒ'].fill('โ—') โŸผ ['โ—','โ—','โ—']
['โ– ','โ—','โ–ฒ'].reverse() โŸผ ['โ–ฒ','โ—','โ– ']
['โ– ','โ—','โ– '].sort()    โŸผ ['โ– ','โ– ','โ—']

Finding Array elements:

['โ– ','โ—','โ– '].includes('โ– ')           โŸผ true
['โ– ','โ—','โ– '].indexOf('โ– ')            โŸผ 0
['โ– ','โ—','โ– '].lastIndexOf('โ– ')        โŸผ 2
['โ– ','โ—','โ– '].find(x => x==='โ– ')      โŸผ 'โ– '
['โ– ','โ—','โ– '].findIndex(x => x==='โ– ') โŸผ 0

Listing elements (spreading via ... is needed because the methods return iterables):

[...['โ– ','โ—','โ–ฒ'].keys()]    โŸผ [0,1,2]
[...['โ– ','โ—','โ–ฒ'].values()]  โŸผ ['โ– ','โ—','โ–ฒ']
[...['โ– ','โ—','โ–ฒ'].entries()] โŸผ [[0,'โ– '],[1,'โ—'],[2,'โ–ฒ']]

Adding or removing an element at either end of an Array:

arr=['โ– ','โ—'];     arr.push('โ–ฒ');    arr โŸผ ['โ– ','โ—','โ–ฒ']
arr=['โ– ','โ—','โ–ฒ']; arr.pop();        arr โŸผ ['โ– ','โ—']

arr=['โ– ','โ—'];     arr.unshift('โ–ฒ'); arr โŸผ ['โ–ฒ','โ– ','โ—']
arr=['โ–ฒ','โ– ','โ—']; arr.shift();      arr โŸผ ['โ– ','โ—']

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