faster array manipulations (observablehq#861)

Fil · web-flow · commit 8e30e22bea6d · 2022-05-06T21:13:28.000-07:00
use a tight loop to create index ranges (data has always been arrayified)
diff --git a/src/options.js b/src/options.js
@@ -127,7 +127,10 @@ export function maybeZ({z, fill, stroke} = {}) {
 
 // Returns a Uint32Array with elements [0, 1, 2, &hellip; data.length - 1].
 export function range(data) {
-  return Uint32Array.from(data, indexOf);
+  const n = data.length;
+  const r = new Uint32Array(n);
+  for (let i = 0; i < n; ++i) r[i] = i;
+  return r;
 }
 
 // Returns a filtered range of data given the test function.
