Append values to javascript dictionary
Another alternative:
const input = [{ "key": "foo", "val": 3 }, { "key": "bar", "val": 10 }, { "key": "foo", "val": 100 }, { "key": "baz", "val": 99 }, { "key": "biff", "val": 10 }, { "key": "foo", "val": 77 }]
const dict = {}
input.forEach(({ key, val }) =>
key in dict ? dict[key].push(val) : dict[key] = [val] )
console.log(dict);
And a one-liner, with immutability
input.reduce((dict, { key, val }) => ({ ...dict, [key]: [...dict[key] || [], val] }), {})
for (var i = 0; i < input.length; i++) {
var datum = input[i];
if (!d[datum.key]) {
d[datum.key] = [];
}
d[datum.key].push(datum.val);
}
FYI, you shouldn't use for (var i in input)
to iterate over an array.
Another way, with reduce
.
var d = input.reduce(function (res, item) {
var key = item.key;
if (!res[key]) res[key] = [item.val];
else res[key].push(item.val);
return res;
}, {});