if I had an array of objects such as
const arrOfObj = [
{
'a': 'a',
'b': 'b',
'c': 'c',
'd': 'd'
}
]
how do I create a new array with an object that has only a and b?
{
'a': 'a',
'b': 'b'
}
I've been trying something like
Object.entries(arrOfObjs[0]).filter(x => x[0] !== 'a' && x[0] !== 'b')
but there must be a simpler cleaner way
You can map the array, use destructuring and shorthand property names you're there:
const result = arrOfObj.map(({a, b}) => ({a, b}));
Example:
const arrOfObj = [
{ 'a': 'a', 'b': 'b', 'c': 'c', 'd': 'd' },
{ 'a': 'aa', 'b': 'bb', 'c': 'cc', 'd': 'dd' },
{ 'a': 'aaa', 'b': 'bbb', 'c': 'ccc', 'd': 'ddd' }
];
const result = arrOfObj.map(({a, b}) => ({a, b}));
console.log(result);Destructuring syntax works nicely for this, as you can see in the other answer. However it requires a and b at the program level. If a and b exist at the data level, for example as values in array, the program would be slightly different
const pick = (o = {}, keys = []) =>
keys .reduce
( (acc, k) => Object .assign (acc, { [k]: o[k] })
, {}
)
const print = (...values) =>
values .forEach (x => console .log (x))
const data =
{ a: 1, b: 2, c: 3 }
print
( pick (data, [ 'a', 'b' ]) // { a: 1, b: 2 }
, pick (data, [ 'c', 'd' ]) // { c: 3, d: undefined }
, pick (data, []) // {}
, data // { a: 1, b: 2, c: 3 }
)As you can see, data is not mutated by use of pick.
c and d properties, then we could write a similar function, omit.
omit. Thanks for the comment Scott. It means a lot coming from you. I haven't seen such a style guide but I've been heavily influenced by Scheme and ML languages like OCaml and Elm. Maybe we could make a draft? I've never done anything like that before. Could be fun :DYour title suggests that you want to remove specific properties, but the text suggests you actually want to keep specific ones. If it's the latter, I would suggest either the solution from ibrahim mahrir or the one from user633183.
But if it's the former, here is an approach similar to the one from user633183 but that creates a clone without the given properties:
const omit = (keys = []) => (o = {}) =>
Object .keys (o) .reduce
( (acc, k) => keys .includes (k)
? acc
: Object .assign (acc, { [k]: o[k] })
, {}
)
const print = (...values) =>
values .forEach (x => console .log (x))
const data =
{ a: 1, b: 2, c: 3, d: 4 }
print
( omit ([ 'c', 'd' ]) (data) // { a: 1, b: 2 }
, omit ([ 'b' ]) (data) // { a: 1, c: 3, d: 4 }
, omit ([ ]) (data) // { a: 1, b: 2, c: 3, d: 4 }
, data // { a: 1, b: 2, c: 3, d: 4 }
)You can delete properties from an object.
const arrOfObj = [
{
'a': 'a',
'b': 'b',
'c': 'c',
'd': 'd'
}
];
console.log(arrOfObj.reduce((acc, val) => {
let v = Object.assign({}, val);
Object.keys(v).forEach(i => {
if (i !== 'a' && i !== 'b') {
delete v[i];
}
});
acc.push(v);
return acc;
}, []));
console.log(arrOfObj);** Edited the above to stay more inline with the request.
arrOfObj