Replace instanceof checks to work across color.js sources

src/ColorSpace.js

@@ -3,7 +3,7 @@
  * Defines the class and other types related to creating color spaces.
  * For the builtin color spaces, see the `spaces` module.
  */
-import { type, isNone } from "./util.js";
+import { type, isNone, isInstance } from "./util.js";
 import Format from "./Format.js";
 import {getWhite} from "./adapt.js";
 import hooks from "./hooks.js";
@@ -294,7 +294,7 @@ export default class ColorSpace {
 	 * @param {ColorSpace | string} name
 	 */
 	static get (space, ...alternatives) {
-		if (!space || space instanceof ColorSpace) {
+		if (!space || isInstance(space, this)) {
 			return space;
 		}
 

src/Format.js

@@ -1,4 +1,4 @@
-import { isNone } from "./util.js";
+import { isInstance, isNone } from "./util.js";
 import Type from "./Type.js";
 
 // Type "imports"
@@ -131,13 +131,14 @@ export default class Format {
 		return this.type === "function" || /** @type {any} */ (this).serialize;
 	}
 
+
 	/**
 	 * @param {Format | FormatInterface} format
 	 * @param {RemoveFirstElement<ConstructorParameters<typeof Format>>} args
 	 * @returns {Format}
 	 */
 	static get (format, ...args) {
-		if (!format || format instanceof Format) {
+		if (!format || isInstance(format, this)) {
 			return /** @type {Format} */ (format);
 		}
 

src/Type.js

@@ -1,4 +1,4 @@
-import { serializeNumber, mapRange } from "./util.js";
+import { serializeNumber, mapRange, isInstance } from "./util.js";
 
 export default class Type {
 	// Class properties - declared here so that type inference works
@@ -117,10 +117,10 @@
 	}
 
 	static get (type, ...args) {
-		if (type instanceof this) {
+		if (isInstance(type, this)) {
 			return type;
 		}
 
 		return new this(type, ...args);
 	}
 }

src/color.js

@@ -122,7 +122,7 @@ export default class Color {
 	 * Basically gets us the same result as new Color(color) but doesn't clone an existing color object
 	 */
 	static get (color, ...args) {
-		if (color instanceof Color) {
+		if (util.isInstance(color, this)) {
 			return color;
 		}
 

src/getColor.js

@@ -1,5 +1,5 @@
 import ColorSpace from "./ColorSpace.js";
-import {isString} from "./util.js";
+import {isString, isInstance} from "./util.js";
 import parse from "./parse.js";
 
 // Type "imports"
@@ -37,7 +37,7 @@ export default function getColor (color, options) {
 	// Object fixup
 	let space = color.space || color.spaceId;
 
-	if (!(space instanceof ColorSpace)) {
+	if (!isInstance(space, ColorSpace)) {
 		// Convert string id to color space object
 		color.space = ColorSpace.get(space);
 	}

src/util.js

@@ -172,3 +172,34 @@ export function bisectLeft (arr, value, lo = 0, hi = arr.length) {
 	}
 	return lo;
 }
+
+/**
+ * Determines whether an argument is an instance of a constructor, including subclasses.
+ * This is done by first just checking `instanceof`,
+ * and then comparing the string names of the constructors if that fails.
+ * @param {any} arg
+ * @param {C} constructor
+ * @template {new (...args: any) => any} C
+ * @returns {arg is InstanceType<C>}
+ */
+export function isInstance (arg, constructor) {
+	if (arg instanceof constructor) {
+		return true;
+	}
+
+	const targetName = constructor.name;
+
+	while (arg) {
+		const proto = Object.getPrototypeOf(arg);
+		const constructorName = proto?.constructor?.name;
+		if (constructorName === targetName) {
+			return true;
+		}
+		if (!constructorName || constructorName === "Object") {
+			return false;
+		}
+		arg = proto;
+	}
+
+	return false;
+}

types/test/util.ts

@@ -5,6 +5,7 @@ import {
 	interpolate,
 	interpolateInv,
 	mapRange,
+	isInstance,
 } from "colorjs.io/src/util";
 
 isString("foo"); // $ExpectType boolean
@@ -46,3 +47,11 @@ mapRange([1, 2], [3, 4]);
 mapRange([1, 2, 3], [4, 5, 6], 7);
 
 mapRange([1, 2], [3, 4], 5); // $ExpectType number
+
+class SomeClass {}
+
+declare const instance: any;
+
+if (isInstance(instance, SomeClass)) {
+	instance; // $ExpectType SomeClass
+}