I have the following array of objects:
var array = [ {'a': '12', 'b':'10'}, {'a': '20', 'b':'22'} ]; How can I add a new property c = b - a to all objects of the array?
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2 Answers
you can use array.map,
and you should use Number() to convert props to numbers for adding:
var array = [ {'a': '12', 'b':'10'}, {'a': '20', 'b':'22'} ]; var r = array.map( x => { x.c = Number(x.b) - Number(x.a); return x }) console.log(r)And, with the support of the spread operator, a more functional approach would be:
array.map(x => ({ ...x, c: Number(x.a) - Number(x.b) })) 4 Comments
georg
don't understand the DV either - both
map and Number are preferred for stuff like this over forEach and + respectively.
isvforall
OP wants
c = b - a
maioman
@isvforall ok, thanks for the edit;
oomer
just to add a small detail, with the spread operator you still need to assign it to
var r, the array array is not mutated.Use forEach function:
var array = [{ 'a': '12', 'b': '10' }, { 'a': '20', 'b': '22' }]; array.forEach(e => e.c = +e.b - +e.a); console.log(JSON.stringify(array));
7 Comments
Mritunjay
shouldn't you try ES5 way
Miguel Moura
Are lambda expressions " =>" available in ES5?
isvforall
@Miguel no, it's ES6, I edited with ES5 now
Andy
@Mritunjay I think if the OP can't be bothered to try to solve the problem themself they should accept the answers they get, whether ES5 or ES6.
Mritunjay
@Andy I agree, but I would say if it's not asked I would prefer being answered in ES5 way only. There are a lot of people who will view answers and might get confused.
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