find duplicates in array
function findDuplicates(arr) {
const duplicates = new Set()
return arr.filter(item => {
if (duplicates.has(item)) {
return true
}
duplicates.add(item)
return false
})
}find duplicates in array
function findDuplicates(arr) {
const duplicates = new Set()
return arr.filter(item => {
if (duplicates.has(item)) {
return true
}
duplicates.add(item)
return false
})
}js find duplicates in array
const names = ['Mike', 'Matt', 'Nancy', 'Adam', 'Jenny', 'Nancy', 'Carl']
const count = names =>
names.reduce((a, b) => ({ ...a,
[b]: (a[b] || 0) + 1
}), {}) // don't forget to initialize the accumulator
const duplicates = dict =>
Object.keys(dict).filter((a) => dict[a] > 1)
console.log(count(names)) // { Mike: 1, Matt: 1, Nancy: 2, Adam: 1, Jenny: 1, Carl: 1 }
console.log(duplicates(count(names))) // [ 'Nancy' ]Copyright © 2021 Codeinu
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