Example 1: count duplicates array js
uniqueCount = ["a","b","c","d","d","e","a","b","c","f","g","h","h","h","e","a"];
var count = {};
uniqueCount.forEach(function(i) { count[i] = (count[i]||0) + 1;});
console.log(count);
Example 2: how to get duplicate values from array in javascript
var array = [1, 2, 2, 3, 3, 4, 5, 6, 2, 3, 7, 8, 5, 22, 1, 2, 511, 12, 50, 22];
console.log([...new Set(
array.filter((value, index, self) => self.indexOf(value) !== index))]
);
Example 3: how to get duplicate values from array in javascript
var names = ['Mike', 'Matt', 'Nancy', 'Adam', 'Jenny', 'Nancy', 'Carl']
var uniq = names
.map((name) => {
return {
count: 1,
name: name
}
})
.reduce((a, b) => {
a[b.name] = (a[b.name] || 0) + b.count
return a
}, {})
var duplicates = Object.keys(uniq).filter((a) => uniq[a] > 1)
console.log(duplicates)
Example 4: javascript get duplicates in array
function getDuplicateArrayElements(arr){
var sorted_arr = arr.slice().sort();
var results = [];
for (var i = 0; i < sorted_arr.length - 1; i++) {
if (sorted_arr[i + 1] === sorted_arr[i]) {
results.push(sorted_arr[i]);
}
}
return results;
}
var colors = ["red","orange","blue","green","red","blue"];
var duplicateColors= getDuplicateArrayElements(colors);
Example 5: duplicate numbers in an array javascript
[1, 1, 2, 2, 3].filter((element, index, array) => array.indexOf(element) !== index)
Example 6: check for duplicates in array javascript
[1, 2, 3].every((e, i, a) => a.indexOf(e) === i)
[1, 2, 1].every((e, i, a) => a.indexOf(e) === i)