var obj = { 1: [1,2,4,3], 2: [2,3,4,5], 3: [4,5,6] } Object.values(obj).reduce((a,b) => [...a, ...b], [])
[].reduce.call( Object.assign(arrObj, { length: 14 }), (accumalate, current) => accumalate.concat(current) );