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@lcherone

lcherone/script.js

Last active Jun 26, 2020
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Javascript merge multiple arrays, de-duped by property name, O(N1) using reduce
const array1 = [
{ name: 'a', creationDate: new Date() },
{ name: 'b', creationDate: new Date() },
]
const array2 = [
{ name: 'a', creationDate: new Date() },
{ name: 'c', creationDate: new Date() },
]
const mergeBy = (...arrays) => {
const prop_index = arrays.length - 1, key = arrays[prop_index]
if (typeof arrays[prop_index] !== 'string') throw Error('Last argument must be a string')
arrays.splice(-1, 1)
return Object.values(
arrays.reduce((acc, cur) => {
cur.forEach(prop => acc[prop[key]] = acc[prop[key]] ? Object.assign(acc[prop[key]], prop) : prop)
return acc
}, {})
)
}
console.log('--------')
console.log(mergeBy(array1, array2, 'name'))
console.log('--------')
console.log(mergeBy(array1, array2, 'creationDate'))
// .etc:
// console.log(mergeBy(array1, array2, array3, 'name'))
// console.log(mergeBy(array1, array2, array3, array4, 'name'))
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