.map .reduce .filter

whAT are the main work of these .map and .reduce and .filter

and why we use arrow (item) =>
can somebody explain .
the use of arrow

See the following challenges which discuss these methods.

See the following challenge related to arrow functions.


Arrow functions aren’t necessary for .map, .reduce, or .filter, nor the other way around. Arrow functions are (for most purposes) simply a more concise syntax for writing functions.

const ANIMAL_EMOJIS = ['🐢', '🐈', '🐒', 'πŸ¦„', 'πŸ•', '🐟'];

// the following two versions both return ['🐢', 'πŸ•']

// version 1:
function isDogEmoji(str) {
  return str === '🐢' || str === 'πŸ•';


//version 2:
ANIMAL_EMOJIS.filter(str => str === '🐢' || str === 'πŸ•');