Nodejs Distinct Array Items

nodejs-distinct-array-items

const diff = (arr1, arr2) => [
  ...arr1.filter(e => !arr2.includes(e)),
  ...arr2.filter(e => !arr1.includes(e))
];

const sym = (...args) => [...new Set(args.reduce(diff))];

sym([1, 2, 3], [5, 2, 1, 4]);

// ===========================
// Explanation (individually)
// The code above works by filtering out distinct items from each array in the diff function. Those items are then returned in a single array. Then the single array is reduced to unique items.
const arr2Distinct = [...[5, 2, 1, 4].filter(e => ![1, 2 ,3].includes(e))]
//console.log("arr2Distinct", arr2Distinct)
// result: [ 5, 4 ] 

const arr1Distinct = [...[1, 2, 3].filter(e => ![5, 2, 1, 4].includes(e))]
//console.log("arr1Distinct", arr1Distinct)
// result: [ 3 ]

const combinedArrays = [...arr1Distinct, ...arr2Distinct]
//console.log("combinedArrays", combinedArrays)
// result: [ 3, 4, 5 ]

// dedupe the arrays
const dedupedArrays = [...new Set(combinedArrays)]
///console.log("dedupedArrays: ", dedupedArrays)

References:
// ...args spreads the args 
// see: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Spread_syntax
// https://forum.freecodecamp.org/t/freecodecamp-challenge-guide-find-the-symmetric-difference/301611a