Example 1: javascript remove duplicate in arrays
// 1. filter()
function removeDuplicates(array) {
return array.filter((a, b) => array.indexOf(a) === b)
};
// 2. forEach()
function removeDuplicates(array) {
let x = {};
array.forEach(function(i) {
if(!x[i]) {
x[i] = true
}
})
return Object.keys(x)
};
// 3. Set
function removeDuplicates(array) {
array.splice(0, array.length, ...(new Set(array)))
};
// 4. map()
function removeDuplicates(array) {
let a = []
array.map(x =>
if(!a.includes(x) {
a.push(x)
})
return a
};
/THIS SITE/ "https://dev.to/mshin1995/back-to-basics-removing-duplicates-from-an-array-55he#comments"
Example 2: 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 3: find duplicates and their count in an array javascript
var counts = {};
your_array.forEach(function(x) { counts[x] = (counts[x] || 0)+1; });
Example 4: how to get duplicate values from array in javascript
let a = [1, 2, 3, 4, 2, 2, 4, 1, 5, 6]
let b = [...new Set(a.sort().filter((o, i) => o !== undefined && a[i + 1] !== undefined && o === a[i + 1]))]
// b is now [1, 2, 4]
Example 5: 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);//["blue", "red"]
Example 6: duplicate numbers in an array javascript
[1, 1, 2, 2, 3].filter((element, index, array) => array.indexOf(element) !== index) // [1, 2]