fix: Restore ES5 compatibility

by adding a ponyfill for `Array.prototype.find` to conventions
and converting `let` to `var`

lib/conventions.js

@@ -1,5 +1,35 @@
 'use strict';
 
+/**
+ * Ponyfill for `Array.prototype.find` which is only available in ES6 runtimes.
+ *
+ * @template {unknown} T
+ * @param {Array<T> | ({length:number, [number]: T})} list
+ * @param {function (item: T, index: number, list:Array<T> | ({length:number, [number]: T})):boolean} predicate
+ * @param {Partial<Pick<ArrayConstructor['prototype'], 'find'>>?} ac `Array.prototype` by default,
+ * 				allows injecting a custom implementation in tests
+ * @returns {T | undefined}
+ *
+ * @see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/find
+ * @see https://tc39.es/ecma262/multipage/indexed-collections.html#sec-array.prototype.find
+ */
+function find(list, predicate, ac) {
+	if (ac === undefined) {
+		ac = Array.prototype;
+	}
+	if (list && typeof ac.find === 'function') {
+		return ac.find.call(list, predicate);
+	}
+	for (var i = 0; i < list.length; i++) {
+		if (Object.prototype.hasOwnProperty.call(list, i)) {
+			var item = list[i];
+			if (predicate.call(undefined, item, i, list)) {
+				return item;
+			}
+		}
+	}
+}
+
 /**
  * "Shallow freezes" an object to render it immutable.
  * Uses `Object.freeze` if available,
@@ -330,6 +360,7 @@ var NAMESPACE = freeze({
 });
 
 exports.assign = assign;
+exports.find = find;
 exports.freeze = freeze;
 exports.HTML_BOOLEAN_ATTRIBUTES = HTML_BOOLEAN_ATTRIBUTES;
 exports.HTML_RAW_TEXT_ELEMENTS = HTML_RAW_TEXT_ELEMENTS;

lib/dom.js

@@ -1,6 +1,7 @@
 'use strict';
 
 var conventions = require('./conventions');
+var find = conventions.find;
 var isHTMLRawTextElement = conventions.isHTMLRawTextElement;
 var isHTMLVoidElement = conventions.isHTMLVoidElement;
 var MIME_TYPE = conventions.MIME_TYPE;
@@ -180,14 +181,6 @@ NodeList.prototype = {
 		}
 		return buf.join('');
 	},
-	/**
-	 * @private
-	 * @param {function (Node):boolean} predicate
-	 * @returns {Node | undefined}
-	 */
-	find: function (predicate) {
-		return Array.prototype.find.call(this, predicate);
-	},
 	/**
 	 * @private
 	 * @param {function (Node):boolean} predicate
@@ -832,10 +825,10 @@ function isTextNode(node) {
  */
 function isElementInsertionPossible(doc, child) {
 	var parentChildNodes = doc.childNodes || [];
-	if (parentChildNodes.find(isElementNode) || isDocTypeNode(child)) {
+	if (find(parentChildNodes, isElementNode) || isDocTypeNode(child)) {
 		return false;
 	}
-	var docTypeNode = parentChildNodes.find(isDocTypeNode);
+	var docTypeNode = find(parentChildNodes, isDocTypeNode);
 	return !(child && docTypeNode && parentChildNodes.indexOf(docTypeNode) > parentChildNodes.indexOf(child));
 }
 /**
@@ -870,24 +863,24 @@ function _insertBefore(parent, node, child) {
 	var nodeChildNodes = node.childNodes || [];
 	if (parent.nodeType === Node.DOCUMENT_NODE) {
 		if (node.nodeType === Node.DOCUMENT_FRAGMENT_NODE) {
-			let nodeChildElements = nodeChildNodes.filter(isElementNode);
-			if (nodeChildElements.length > 1 || nodeChildNodes.find(isTextNode)) {
+			var nodeChildElements = nodeChildNodes.filter(isElementNode);
+			if (nodeChildElements.length > 1 || find(nodeChildNodes, isTextNode)) {
 				throw new DOMException(HIERARCHY_REQUEST_ERR, 'More than one element or text in fragment');
 			}
 			if (nodeChildElements.length === 1 && !isElementInsertionPossible(parent, child)) {
 				throw new DOMException(HIERARCHY_REQUEST_ERR, 'Element in fragment can not be inserted before doctype');
 			}
 		}
 		if (isElementNode(node)) {
-			if (parentChildNodes.find(isElementNode) || !isElementInsertionPossible(parent, child)) {
+			if (find(parentChildNodes, isElementNode) || !isElementInsertionPossible(parent, child)) {
 				throw new DOMException(HIERARCHY_REQUEST_ERR, 'Only one element can be added and only after doctype');
 			}
 		}
 		if (isDocTypeNode(node)) {
-			if (parentChildNodes.find(isDocTypeNode)) {
+			if (find(parentChildNodes, isDocTypeNode)) {
 				throw new DOMException(HIERARCHY_REQUEST_ERR, 'Only one doctype is allowed');
 			}
-			let parentElementChild = parentChildNodes.find(isElementNode);
+			var parentElementChild = find(parentChildNodes, isElementNode);
 			if (child && parentChildNodes.indexOf(parentElementChild) < parentChildNodes.indexOf(child)) {
 				throw new DOMException(HIERARCHY_REQUEST_ERR, 'Doctype can only be inserted before an element');
 			}

test/conventions/find.test.js

@@ -0,0 +1,24 @@
+'use strict';
+
+const { find } = require('../../lib/conventions');
+
+describe('find', () => {
+	it('should work in node without pasing an ArrayConstructor', () => {
+		const predicate = jest.fn((item) => item === 'b');
+		const list = ['a', 'b', 'c'];
+
+		expect(find(list, predicate)).toBe('b');
+		expect(predicate).toHaveBeenCalledTimes(2);
+		expect(predicate).toHaveBeenCalledWith('a', 0, list);
+		expect(predicate).toHaveBeenCalledWith('b', 1, list);
+	});
+	it('should work when ArrayConstructor does not provide find', () => {
+		const predicate = jest.fn((item) => item === 'b');
+		const list = ['a', 'b', 'c'];
+
+		expect(find(list, predicate, {})).toBe('b');
+		expect(predicate).toHaveBeenCalledTimes(2);
+		expect(predicate).toHaveBeenCalledWith('a', 0, list);
+		expect(predicate).toHaveBeenCalledWith('b', 1, list);
+	});
+});