mobile typing isn't scored — practice only
function groupBy(items, key) {
JavaScript · general · type the snippet below to practice
def fib(n):
a, b = 0, 1
for _ in range(n):
a, b = b, a + b
return a
about this snippet
This is the groupby snippet in JavaScript — 8 lines of real JavaScript code that exercises common patterns you'll see in production. DeveloperType scores you on net WPM and accuracy and only counts runs above 95% accuracy on the leaderboard, so practice rewards precision, not speed alone.
view source (8 lines)
function groupBy(items, key) {
return items.reduce((acc, item) => {
const k = typeof key === "function" ? key(item) : item[key];
(acc[k] ||= []).push(item);
return acc;
}, {});
}
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