I'm playing around with the limits of array and arrow functions and I'm trying to convert this reduce function into an arrow function:
var monthsById = months.reduce(function(result, month) {
result[month.Id] = month;
return result;
}, {});
But I'm having trouble to return the map, since result[month.Id] = month;
will return the month and not the map like in this approach:
var monthsById = months.reduce((byId, month) => byId[month.Id] = month, {});
So I'm looking for a single statement, that sets the value AND returns the object. ( new Map()
is not an option, since I need it in the regular {}
format).
var months = [ { Id: 1 }, { Id: 2 }, { Id: 3 } ]; var monthsById = months.reduce((byId, month) => byId[month.Id] = month, {}); console.log(monthsById);
You can return byId
in each iteration and wrap function body in parentheses ()
var months = [ { Id: 1 }, { Id: 2 }, { Id: 3 } ]; var monthsById = months.reduce((byId, month) => (byId[month.Id] = month, byId), {}); console.log(monthsById);
You could use Object.assign
where you set a new property with computed property names and return the whole object.
var months = [{ Id: 1 }, { Id: 2 }, { Id: 3 }], monthsById = months.reduce((byId, month) => Object.assign(byId, { [month.Id]: month }), {}); console.log(monthsById);
An example with spreading.
var months = [{ Id: 1 }, { Id: 2 }, { Id: 3 }], monthsById = months.reduce((byId, month) => ({ ...byId, [month.Id]: month }), {}); console.log(monthsById);
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