var a = [{a:1, b: 11}, {a: 2, b: 22}]
let r = a.reduce((p, n) => {
    Object.entries(n).forEach(([k,v], i) => {
           if (!p[k])  p[k] = [v]
           else{
               p[k].push(v)
           }
    })
    return p
}, {})

console.log(JSON.stringify(r))



/// output:

// {"a":[1,2],"b":[11,22]}