Flatten Nested Array in JavaScript – Convert Nested Array to single dimensional array

const arr = [[1, 2], [3, 4], [5, 6]];

const flat = arr.reduce((acc, curr) => {
    return acc.concat(curr);
}, []);

console.log(flat);
// Output : [1,2,3,4,5,6];



const city = [['bangalore', 'pune'], ['chennai', 'kolkata'], ['delhi', 'patna'], ['mumbai']];

const combinedArray = city.reduce((acc, curr) => {
    return acc.concat(curr);
}, []);

console.log(combinedArray);
// output : ['bangalore','pune','chennai','kolkata','delhi','patna','mumbai']