function flatten(arr) { let flat = [] for(let prop of arr){ if(Array.isArray(prop)){ flat.push(...flattan(prop)) } else { flat.push(prop) } } return flat }
function flatten(arr) { let flat = [] for(let prop of arr){ if(Array.isArray(prop)){ flat.push(...flattan(prop)) } else { flat.push(prop) } } return flat }