var array = [[1, 2], [3, 4], [5, 6]].reduce(( pre, next ) => {
return pre.concat(next)
}, []);
console.log(array) // [1, 2, 3, 4, 5, 6]
var array = [[1, 2], [3, 4], [5, 6]].reduce(( pre, next ) => {
return pre.concat(next)
}, []);
console.log(array) // [1, 2, 3, 4, 5, 6]