Index by key in TypeScript

Indexes an array into a record keyed by one of its fields.

function keyBy<T, K extends string>(
  items: T[],
  keyFn: (item: T) => K,
): Record<K, T> {
  const out = {} as Record<K, T>;
  for (const item of items) {
    out[keyFn(item)] = item;
  }
  return out;
}

Keywords and builtins used here

T
as
const
extends
for
function
of
return
string

The run, in numbers

Lines: 10
Characters to type: 190
Tokens: 71
Three-star pace: 105 tpm

At the three-star pace of 105 tokens a minute, this run takes about 41 seconds.

Type this snippet

Step 3 of 11 in Generic helpers, step 11 of 20 in Generics.

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