Core: Migrate from AMD to ES modules 🎉

Migrate all source AMD modules to ECMAScript modules. The final bundle
is compiled by a custom build process that uses Rollup under the hood.

Test files themselves are still loaded via RequireJS as that has to work in
IE 11.

Tests can now be run in "Load as modules" mode which replaces the previous
"Load with AMD" option. That option of running tests doesn't work in IE
and Edge as it requires support for dynamic imports.

Some of the changes required by the migration:
* check `typeof` of `noGlobal` instead of using the variable directly
  as it's not available when modules are used
* change the nonce module to be an object as ECMASscript module exports
  are immutable
* remove some unused exports
* import `./core/parseHTML.js` directly in `jquery.js` so that it's not
  being cut out when the `ajax` module is excluded in a custom compilation

Closes gh-4541

14 files changed, 83 insertions, 158 deletions

diff --git a/src/core/DOMEval.js b/src/core/DOMEval.js
index df83cca52..b0238fd69 100644
--- a/src/core/DOMEval.js
+++ b/src/core/DOMEval.js
@@ -1,43 +1,39 @@
-define( [
-	"../var/document"
-], function( document ) {
-	"use strict";
+import document from "../var/document.js";
 
-	var preservedScriptAttributes = {
-		type: true,
-		src: true,
-		nonce: true,
-		noModule: true
-	};
+var preservedScriptAttributes = {
+	type: true,
+	src: true,
+	nonce: true,
+	noModule: true
+};
 
-	function DOMEval( code, node, doc ) {
-		doc = doc || document;
+function DOMEval( code, node, doc ) {
+	doc = doc || document;
 
-		var i, val,
-			script = doc.createElement( "script" );
+	var i, val,
+		script = doc.createElement( "script" );
 
-		script.text = code;
-		if ( node ) {
-			for ( i in preservedScriptAttributes ) {
+	script.text = code;
+	if ( node ) {
+		for ( i in preservedScriptAttributes ) {
 
-				// Support: Firefox <=64 - 66+, Edge <=18+
-				// Some browsers don't support the "nonce" property on scripts.
-				// On the other hand, just using `getAttribute` is not enough as
-				// the `nonce` attribute is reset to an empty string whenever it
-				// becomes browsing-context connected.
-				// See https://github.com/whatwg/html/issues/2369
-				// See https://html.spec.whatwg.org/#nonce-attributes
-				// The `node.getAttribute` check was added for the sake of
-				// `jQuery.globalEval` so that it can fake a nonce-containing node
-				// via an object.
-				val = node[ i ] || node.getAttribute && node.getAttribute( i );
-				if ( val ) {
-					script.setAttribute( i, val );
-				}
+			// Support: Firefox <=64 - 66+, Edge <=18+
+			// Some browsers don't support the "nonce" property on scripts.
+			// On the other hand, just using `getAttribute` is not enough as
+			// the `nonce` attribute is reset to an empty string whenever it
+			// becomes browsing-context connected.
+			// See https://github.com/whatwg/html/issues/2369
+			// See https://html.spec.whatwg.org/#nonce-attributes
+			// The `node.getAttribute` check was added for the sake of
+			// `jQuery.globalEval` so that it can fake a nonce-containing node
+			// via an object.
+			val = node[ i ] || node.getAttribute && node.getAttribute( i );
+			if ( val ) {
+				script.setAttribute( i, val );
 			}
 		}
-		doc.head.appendChild( script ).parentNode.removeChild( script );
 	}
+	doc.head.appendChild( script ).parentNode.removeChild( script );
+}
 
-	return DOMEval;
-} );
+export default DOMEval;
diff --git a/src/core/access.js b/src/core/access.js
index e088a6557..4eaec4695 100644
--- a/src/core/access.js
+++ b/src/core/access.js
@@ -1,9 +1,5 @@
-define( [
-	"../core",
-	"../core/toType"
-], function( jQuery, toType ) {
-
-"use strict";
+import jQuery from "../core.js";
+import toType from "../core/toType.js";
 
 // Multifunctional method to get and set values of a collection
 // The value/s can optionally be executed if it's a function
@@ -66,6 +62,4 @@ var access = function( elems, fn, key, value, chainable, emptyGet, raw ) {
 	return len ? fn( elems[ 0 ], key ) : emptyGet;
 };
 
-return access;
-
-} );
+export default access;
diff --git a/src/core/camelCase.js b/src/core/camelCase.js
index 61ed90d05..f12a2c67d 100644
--- a/src/core/camelCase.js
+++ b/src/core/camelCase.js
@@ -1,7 +1,3 @@
-define( [], function() {
-
-"use strict";
-
 // Matches dashed string for camelizing
 var rdashAlpha = /-([a-z])/g;
 
@@ -15,6 +11,4 @@ function camelCase( string ) {
 	return string.replace( rdashAlpha, fcamelCase );
 }
 
-return camelCase;
-
-} );
+export default camelCase;
diff --git a/src/core/init.js b/src/core/init.js
index 71f30e926..c2f35e1f4 100644
--- a/src/core/init.js
+++ b/src/core/init.js
@@ -1,13 +1,9 @@
 // Initialize a jQuery object
-define( [
-	"../core",
-	"../var/document",
-	"./var/rsingleTag",
+import jQuery from "../core.js";
+import document from "../var/document.js";
+import rsingleTag from "./var/rsingleTag.js";
 
-	"../traversing/findFilter"
-], function( jQuery, document, rsingleTag ) {
-
-"use strict";
+import "../traversing/findFilter.js";
 
 // A central reference to the root jQuery(document)
 var rootjQuery,
@@ -123,6 +119,4 @@ init.prototype = jQuery.fn;
 // Initialize central reference
 rootjQuery = jQuery( document );
 
-return init;
-
-} );
+export default init;
diff --git a/src/core/isAttached.js b/src/core/isAttached.js
index 579bcffb2..3857d94a8 100644
--- a/src/core/isAttached.js
+++ b/src/core/isAttached.js
@@ -1,23 +1,20 @@
-define( [
-	"../core",
-	"../var/documentElement",
-	"../selector/contains" // jQuery.contains
-], function( jQuery, documentElement ) {
-	"use strict";
+import jQuery from "../core.js";
+import documentElement from "../var/documentElement.js";
 
-	var isAttached = function( elem ) {
-			return jQuery.contains( elem.ownerDocument, elem );
-		},
-		composed = { composed: true };
+import "../selector/contains.js"; // jQuery.contains
 
-	// Support: IE 9 - 11+, Edge 12 - 18+
-	// Check attachment across shadow DOM boundaries when possible (gh-3504)
-	if ( documentElement.getRootNode ) {
-		isAttached = function( elem ) {
-			return jQuery.contains( elem.ownerDocument, elem ) ||
-				elem.getRootNode( composed ) === elem.ownerDocument;
-		};
-	}
+var isAttached = function( elem ) {
+		return jQuery.contains( elem.ownerDocument, elem );
+	},
+	composed = { composed: true };
 
-	return isAttached;
-} );
+// Support: IE 9 - 11+, Edge 12 - 18+
+// Check attachment across shadow DOM boundaries when possible (gh-3504)
+if ( documentElement.getRootNode ) {
+	isAttached = function( elem ) {
+		return jQuery.contains( elem.ownerDocument, elem ) ||
+			elem.getRootNode( composed ) === elem.ownerDocument;
+	};
+}
+
+export default isAttached;
diff --git a/src/core/nodeName.js b/src/core/nodeName.js
index 8a5f5f036..d10e484bc 100644
--- a/src/core/nodeName.js
+++ b/src/core/nodeName.js
@@ -1,13 +1,7 @@
-define( function() {
-
-"use strict";
-
 function nodeName( elem, name ) {
 
   return elem.nodeName && elem.nodeName.toLowerCase() === name.toLowerCase();
 
 };
 
-return nodeName;
-
-} );
+export default nodeName;
diff --git a/src/core/parseHTML.js b/src/core/parseHTML.js
index 8c5268fb1..15278fa02 100644
--- a/src/core/parseHTML.js
+++ b/src/core/parseHTML.js
@@ -1,11 +1,7 @@
-define( [
-	"../core",
-	"../var/document",
-	"./var/rsingleTag",
-	"../manipulation/buildFragment"
-], function( jQuery, document, rsingleTag, buildFragment ) {
-
-"use strict";
+import jQuery from "../core.js";
+import document from "../var/document.js";
+import rsingleTag from "./var/rsingleTag.js";
+import buildFragment from "../manipulation/buildFragment.js";
 
 // Argument "data" should be string of html
 // context (optional): If specified, the fragment will be created in this context,
@@ -52,7 +48,3 @@ jQuery.parseHTML = function( data, context, keepScripts ) {
 
 	return jQuery.merge( [], parsed.childNodes );
 };
-
-return jQuery.parseHTML;
-
-} );
diff --git a/src/core/ready-no-deferred.js b/src/core/ready-no-deferred.js
index 2c3fc1b84..51f6d7f6b 100644
--- a/src/core/ready-no-deferred.js
+++ b/src/core/ready-no-deferred.js
@@ -1,9 +1,5 @@
-define( [
-	"../core",
-	"../var/document"
-], function( jQuery, document ) {
-
-"use strict";
+import jQuery from "../core.js";
+import document from "../var/document.js";
 
 var readyCallbacks = [],
 	whenReady = function( fn ) {
@@ -89,5 +85,3 @@ if ( document.readyState !== "loading" ) {
 	// A fallback to window.onload, that will always work
 	window.addEventListener( "load", completed );
 }
-
-} );
diff --git a/src/core/ready.js b/src/core/ready.js
index 3abb6c03a..d6c507e41 100644
--- a/src/core/ready.js
+++ b/src/core/ready.js
@@ -1,11 +1,8 @@
-define( [
-	"../core",
-	"../var/document",
-	"../core/readyException",
-	"../deferred"
-], function( jQuery, document ) {
+import jQuery from "../core.js";
+import document from "../var/document.js";
 
-"use strict";
+import "../core/readyException.js";
+import "../deferred.js";
 
 // The deferred used on DOM ready
 var readyList = jQuery.Deferred();
@@ -79,5 +76,3 @@ if ( document.readyState !== "loading" ) {
 	// A fallback to window.onload, that will always work
 	window.addEventListener( "load", completed );
 }
-
-} );
diff --git a/src/core/readyException.js b/src/core/readyException.js
index 72bdd90b5..1b5512c15 100644
--- a/src/core/readyException.js
+++ b/src/core/readyException.js
@@ -1,13 +1,7 @@
-define( [
-	"../core"
-], function( jQuery ) {
-
-"use strict";
+import jQuery from "../core.js";
 
 jQuery.readyException = function( error ) {
 	window.setTimeout( function() {
 		throw error;
 	} );
 };
-
-} );
diff --git a/src/core/stripAndCollapse.js b/src/core/stripAndCollapse.js
index 2b63820da..944a79362 100644
--- a/src/core/stripAndCollapse.js
+++ b/src/core/stripAndCollapse.js
@@ -1,14 +1,10 @@
-define( [
-	"../var/rnothtmlwhite"
-], function( rnothtmlwhite ) {
-	"use strict";
+import rnothtmlwhite from "../var/rnothtmlwhite.js";
 
-	// Strip and collapse whitespace according to HTML spec
-	// https://infra.spec.whatwg.org/#strip-and-collapse-ascii-whitespace
-	function stripAndCollapse( value ) {
-		var tokens = value.match( rnothtmlwhite ) || [];
-		return tokens.join( " " );
-	}
+// Strip and collapse whitespace according to HTML spec
+// https://infra.spec.whatwg.org/#strip-and-collapse-ascii-whitespace
+function stripAndCollapse( value ) {
+	var tokens = value.match( rnothtmlwhite ) || [];
+	return tokens.join( " " );
+}
 
-	return stripAndCollapse;
-} );
+export default stripAndCollapse;
diff --git a/src/core/toType.js b/src/core/toType.js
index c555ef9df..67af8a67f 100644
--- a/src/core/toType.js
+++ b/src/core/toType.js
@@ -1,9 +1,5 @@
-define( [
-	"../var/class2type",
-	"../var/toString"
-], function( class2type, toString ) {
-
-"use strict";
+import class2type from "../var/class2type.js";
+import toString from "../var/toString.js";
 
 function toType( obj ) {
 	if ( obj == null ) {
@@ -15,5 +11,4 @@ function toType( obj ) {
 		typeof obj;
 }
 
-return toType;
-} );
+export default toType;
diff --git a/src/core/var/rhtml.js b/src/core/var/rhtml.js
index d7921aa3b..3dace14c5 100644
--- a/src/core/var/rhtml.js
+++ b/src/core/var/rhtml.js
@@ -1,7 +1 @@
-define( function() {
-
-"use strict";
-
-return ( /HTML$/i );
-
-} );
+export default ( /HTML$/i );
diff --git a/src/core/var/rsingleTag.js b/src/core/var/rsingleTag.js
index 340b80db0..5bf52d568 100644
--- a/src/core/var/rsingleTag.js
+++ b/src/core/var/rsingleTag.js
@@ -1,7 +1,3 @@
-define( function() {
-	"use strict";
-
-	// rsingleTag matches a string consisting of a single HTML element with no attributes
-	// and captures the element's name
-	return ( /^<([a-z][^\/\0>:\x20\t\r\n\f]*)[\x20\t\r\n\f]*\/?>(?:<\/\1>|)$/i );
-} );
+// rsingleTag matches a string consisting of a single HTML element with no attributes
+// and captures the element's name
+export default ( /^<([a-z][^\/\0>:\x20\t\r\n\f]*)[\x20\t\r\n\f]*\/?>(?:<\/\1>|)$/i );