const mapFields = (arr, fields) => arr.map((o) =>
Object.entries(o).reduce((acc, [k, v]) => ({...acc, [fields[k] || k]: v}), {}));
const arr = [{
a: 2,
b: 5,
c: 6
}, {
d: 8,
e: 3,
f: 4
}];
const newArr = mapFields(arr, {
b: 'e',
a: 'w',
f: 'v',
c: 'b'
});