remove null objects from extents

src/LayerCake.svelte

@@ -3,6 +3,7 @@
 	import { writable, derived } from 'svelte/store';
 
 	import makeAccessor from './utils/makeAccessor.js';
+	import filterObject from './utils/filterObject.js';
 	import calcExtents from './lib/calcExtents.js';
 	import calcDomain from './helpers/calcDomain.js';
 	import createScale from './helpers/createScale.js';
@@ -158,7 +159,7 @@
 	$: _zRange.set(zRange);
 	$: _rRange.set(rRange);
 	$: _padding.set(padding);
-	$: _extents.set(extents);
+	$: _extents.set(filterObject(extents));
 	$: _flatData.set(flatData || data);
 
 	/* --------------------------------------------

src/utils/filterObject.js

@@ -0,0 +1,35 @@
+/* --------------------------------------------
+ *
+ * Remove undefined fields from an object
+ *
+ * --------------------------------------------
+ */
+export default function filterObject (obj) {
+	return fromEntries(Object.entries(obj).filter(([key, value]) => {
+		return value !== undefined;
+	}));
+}
+
+function fromEntries(iter) {
+	const obj = {};
+
+	for (const pair of iter) {
+		if (Object(pair) !== pair) {
+			throw new TypeError('iterable for fromEntries should yield objects');
+		}
+
+		// Consistency with Map: contract is that entry has "0" and "1" keys, not
+		// that it is an array or iterable.
+
+		const { '0': key, '1': val } = pair;
+
+		Object.defineProperty(obj, key, {
+			configurable: true,
+			enumerable: true,
+			writable: true,
+			value: val,
+		});
+	}
+
+	return obj;
+}

test/filterObject.js

@@ -0,0 +1,23 @@
+/* globals describe it */
+import * as assert from 'assert';
+import filterObject from '../src/utils/filterObject.js';
+
+const name = 'filterObject';
+
+const tests = [
+	{ args: [{}], expected: {} },
+	{ args: [{x: null, y: undefined}], expected: { x: null } },
+	{ args: [{x: 'a', y: undefined, z: undefined}], expected: { x: 'a' } },
+	{ args: [{x: 'a', y: 'b', z: undefined}], expected: { x: 'a', y: 'b' } },
+];
+
+describe(name, () => {
+	tests.forEach(test => {
+		describe(JSON.stringify(test.args), () => {
+			it(`should equal ${JSON.stringify(test.expected)}`, () => {
+				const actual = filterObject(...test.args);
+				assert.deepStrictEqual(actual, test.expected);
+			});
+		});
+	});
+});