Example 1: java array check duplicates
duplicates = false;
for(i = 0; i < zipcodeList.length; i++) {
for(j = i + 1; k < zipcodeList.length; j++) {
if(j != i && zipcodeList[j] == zipcodeList[i]) {
duplicates = true;
}
}
}
Example 2: 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' ]
Example 3: javascript find duplicate in array
// JavaScript - finds if there is duplicate in an array.
// Returns True or False.
const isThereADuplicate = function(arrayOfNumbers) {
// Create an empty associative array or hash.
// This is preferred,
let counts = {};
// // but this also works. Comment in below and comment out above if you want to try.
// let counts = [];
for(var i = 0; i <= arrayOfNumbers.length; i++) {
// As the arrayOfNumbers is being iterated through,
// the counts hash is being populated.
// Each value in the array becomes a key in the hash.
// The value assignment of 1, is there to complete the hash structure.
// Once the key exists, meaning there is a duplicate, return true.
// If there are no duplicates, the if block completes and returns false.
if(counts[arrayOfNumbers[i]] === undefined) {
counts[arrayOfNumbers[i]] = 1;
} else {
return true;
}
}
return false;
}
Example 4: find duplicate values in array javascript
const findDuplicates = (arr) => {
let sorted_arr = arr.slice().sort(); // You can define the comparing function here.
// JS by default uses a crappy string compare.
// (we use slice to clone the array so the
// original array won't be modified)
let results = [];
for (let i = 0; i < sorted_arr.length - 1; i++) {
if (sorted_arr[i + 1] == sorted_arr[i]) {
results.push(sorted_arr[i]);
}
}
return results;
}
let duplicatedArray = [9, 4, 111, 2, 3, 9, 4, 5, 7];
console.log(`The duplicates in ${duplicatedArray} are ${findDuplicates(duplicatedArray)}`);
Example 5: find-array-duplicates
npm i find-array-duplicates
import duplicates from 'find-array-duplicates'
const names = [
{ 'age': 36, 'name': 'Bob' },
{ 'age': 40, 'name': 'Harry' },
{ 'age': 1, 'name': 'Bob' }
]
duplicates(names, 'name').single()
// => { 'age': 36, 'name': 'Bob' }
Example 6: js find duplicates in array
[1, 2, 2, 4, 3, 4].filter((e, i, a) => a.indexOf(e) !== i) // [2, 4]