expose indexOf, and use Uint32Array (#1456)

src/index.js

@@ -26,7 +26,7 @@ export {Text, text, textX, textY} from "./marks/text.js";
 export {TickX, TickY, tickX, tickY} from "./marks/tick.js";
 export {tree, cluster} from "./marks/tree.js";
 export {Vector, vector, vectorX, vectorY, spike} from "./marks/vector.js";
-export {valueof, column, identity} from "./options.js";
+export {valueof, column, identity, indexOf} from "./options.js";
 export {filter, reverse, sort, shuffle, basic as transform, initializer} from "./transforms/basic.js";
 export {bin, binX, binY} from "./transforms/bin.js";
 export {centroid, geoCentroid} from "./transforms/centroid.js";

src/options.d.ts

@@ -41,3 +41,9 @@ export function column(source?: any): [ChannelTransform, <T>(value: T) => T];
  * ```
  */
 export const identity: ChannelTransform;
+
+/**
+ * A channel transform that returns the zero-based index [0, 1, 2, …] of the
+ * data; often used as a default for mark shorthand.
+ */
+export const indexOf: ChannelTransform;

src/options.js

@@ -38,7 +38,7 @@ function floater(f) {
 }
 
 export const field = (name) => (d) => d[name];
-export const indexOf = (d, i) => i;
+export const indexOf = {transform: range};
 export const identity = {transform: (d) => d};
 export const zero = () => 0;
 export const one = () => 1;

test/marks/cell-test.js

@@ -95,10 +95,7 @@ it("cellX() defaults x to identity and y to null", () => {
   assert.deepStrictEqual(Object.keys(cell.channels), ["fill", "x"]);
   assert.deepStrictEqual(
     Object.values(cell.channels).map((c) => Plot.valueof([1, 2, 3], c.value)),
-    [
-      [1, 2, 3],
-      [0, 1, 2]
-    ]
+    [[1, 2, 3], Uint32Array.of(0, 1, 2)]
   );
   assert.deepStrictEqual(
     Object.values(cell.channels).map((c) => c.scale),
@@ -114,10 +111,7 @@ it("cellY() defaults y to identity and x to null", () => {
   assert.deepStrictEqual(Object.keys(cell.channels), ["fill", "y"]);
   assert.deepStrictEqual(
     Object.values(cell.channels).map((c) => Plot.valueof([1, 2, 3], c.value)),
-    [
-      [1, 2, 3],
-      [0, 1, 2]
-    ]
+    [[1, 2, 3], Uint32Array.of(0, 1, 2)]
   );
   assert.deepStrictEqual(
     Object.values(cell.channels).map((c) => c.scale),

test/marks/text-test.js

@@ -17,11 +17,7 @@ it("text() has the expected defaults", () => {
         c.value
       )
     ),
-    [
-      [1, 3],
-      [2, 4],
-      [0, 1]
-    ]
+    [[1, 3], [2, 4], Uint32Array.of(0, 1)]
   );
   assert.deepStrictEqual(
     Object.values(text.channels).map((c) => c.scale),