optimize for single accessor

src/sort.js

@@ -1,18 +1,25 @@
 import ascending from "./ascending.js";
 import permute from "./permute.js";
 
-export default function sort(values, ...order) {
+export default function sort(values, ...F) {
   if (typeof values[Symbol.iterator] !== "function") throw new TypeError("values is not iterable");
   values = Array.from(values);
-  const [f = ascending] = order;
-  if (f.length === 1 || order.length > 1) {
-    order = order.map(f => values.map(f));
-    return permute(values, values.map((d, i) => i).sort((i, j) => {
-      for (const f of order) {
-        const c = ascending(f[i], f[j]);
-        if (c) return c;
-      }
-    }));
+  let [f = ascending] = F;
+  if (f.length === 1 || F.length > 1) {
+    const index = Uint32Array.from(values, (d, i) => i);
+    if (F.length > 1) {
+      F = F.map(f => values.map(f));
+      index.sort((i, j) => {
+        for (const f of F) {
+          const c = ascending(f[i], f[j]);
+          if (c) return c;
+        }
+      });
+    } else {
+      f = values.map(f);
+      index.sort((i, j) => ascending(f[i], f[j]));
+    }
+    return permute(values, index);
   }
   return values.sort(f);
 }