// Given an array, return the first recurring number
function firstRecurringNumber(arr) {
if (!arr || arr.length === 0) {
return undefined;
}
const numbers = new Map();
for (const item of arr) {
if (!numbers.get(item)) {
numbers.set(item, 1);
} else {
return item;
// numbers.set(item, numbers.get(item) + 1);
}
}
return undefined;
}
console.log(firstRecurringNumber([2,5,1,2,3,5,1,2,4]));
console.log(firstRecurringNumber([2,1,1,2,3,5,1,2,4]));
console.log(firstRecurringNumber([2,3,4,5]));
console.log(firstRecurringNumber([]));
