js check if element repeated code example
Example 1: how to check for duplicate syntax in javascript
let strArray = [ "q", "w", "w", "w", "e", "i", "u", "r"];
let findDuplicates = arr => arr.filter((item, index) => arr.indexOf(item) != index)
console.log(findDuplicates(strArray)) // All duplicates
console.log([...new Set(findDuplicates(strArray))]) // Unique duplicates
Example 2: javascript check if array has duplicates
function hasDuplicates(array) {
return (new Set(array)).size !== array.length;
}