Example 1: check if array has same values javascript
const allEqual = arr => arr.every(v => v === arr[0]);
allEqual([1,1,1,1]);
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: javascript check if array has duplicates
function hasDuplicates(array) {
return (new Set(array)).size !== array.length;
}
Example 4: 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)
Example 5: how to count duplicates in an array javascript
arr.reduce((b,c)=>((b[b.findIndex(d=>d.el===c)]||b[b.push({el:c,count:0})-1]).count++,b),[]);
Example 6: check for duplicates in array javascript
[1, 2, 2, 4, 3, 4].filter((e, i, a) => a.indexOf(e) !== i)