Press "Push" to generate a new programatic undo event.
22 |
Use your browser's undo behavior (Ctrl/Cmd-Z) to undo or redo (Ctrl/Cmd-Shift-Z).
23 |
Type into the text input to intersperse 'traditional' events with programatic events.
24 |
25 |
26 |
27 |
28 |
29 |
30 |
31 |
32 |
33 |
--------------------------------------------------------------------------------
/element.js:
--------------------------------------------------------------------------------
1 |
2 | import {Undoer} from './undoer.js';
3 |
4 |
5 | const useShadowDOM = false && Element.prototype.attachShadow;
6 |
7 |
8 | export default class UndoerElement extends HTMLElement {
9 |
10 | static get observedAttributes() {
11 | return ['state'];
12 | }
13 |
14 | constructor() {
15 | super();
16 | this._root = useShadowDOM ? this.attachShadow({mode: 'open'}) : this;
17 |
18 | // hide from the first attributeChangedCallback call
19 | this._selfAttributeChange = true;
20 | window.setTimeout(() => {
21 | this._selfAttributeChange = false;
22 | });
23 |
24 | const callback = (data) => {
25 | const {value, attr} = data;
26 | this._updateAttribute(attr ? value : null);
27 |
28 | // hooray! tell the client
29 | this.dispatchEvent(new CustomEvent('state', {detail: value}));
30 | };
31 |
32 | // set up initial zero undo state from attr
33 | const zero = this.getAttribute('state');
34 | const attr = this.hasAttribute('state');
35 | this._undoer = new Undoer(callback, {value: zero, attr});
36 | }
37 |
38 | attributeChangedCallback(name, oldValue, newValue) {
39 | if (name === 'state' && !this._selfAttributeChange) {
40 | this._internalSet(newValue, true);
41 | }
42 | }
43 |
44 | set state(value) {
45 | if (!this.isConnected) {
46 | throw new Error('can\'t push state while disconnected');
47 | }
48 |
49 | // render if simple "attribute safe" state
50 | const attr = (typeof value === 'string' || typeof value === 'number');
51 | this._internalSet(value, attr);
52 | }
53 |
54 | get state() {
55 | const {value} = this._undoer.data;
56 | return value;
57 | }
58 |
59 | _updateAttribute(value) {
60 | this._selfAttributeChange = true;
61 | try {
62 | if (value) {
63 | this.setAttribute('state', value);
64 | } else {
65 | this.removeAttribute('state');
66 | }
67 | } finally {
68 | this._selfAttributeChange = false;
69 | }
70 | }
71 |
72 | _internalSet(value, attr) {
73 | this._updateAttribute(attr ? value : null);
74 | this._undoer.push({value, attr}, this._root);
75 | }
76 |
77 | };
--------------------------------------------------------------------------------
/README.md:
--------------------------------------------------------------------------------
1 | Native undo/redo behavior for web.
2 | This lets you push native undo stack events onto your pages, so that users can use Ctrl/Cmd-Z—or even use some other gesture (e.g., on iOS devices, you can shake your phone to Undo).
3 |
4 | See a [writeup on how this works](https://dev.to/chromiumdev/-native-undo--redo-for-the-web-3fl3) or an [awesome maze-based demo](https://codepen.io/samthor/pen/WJvLxd) for more.
5 |
6 | ## Usage
7 |
8 | Install on NPM/Yarn via `undoer`.
9 | You can use this element as a Web Component or as pure, imperative JavaScript.
10 |
11 | ### Web Component
12 |
13 | Add the dependency to your JS and register it as a CE:
14 |
15 | ```js
16 | import UndoerElement from './node_modules/undoer/element.js';
17 | customElements.define('undoer-element', UndoerElement);
18 | ```
19 |
20 | Then add the element to your page, optionally adding `state` attribute to set its zero initial state (otherwise it will be `null`):
21 |
22 | ```html
23 |
24 | ```
25 |
26 | Finally, use the element's JavaScript API:
27 |
28 | ```js
29 | const undoerEl = document.querySelector('undoer-element');
30 |
31 | undoerEl.addEventListener('state', (ev) => {
32 | console.info('user undo or redid', ev.detail);
33 | });
34 |
35 | // set new state with
36 | undoerEl.state = 'new state';
37 | undoerEl.state = /* any object */ ;
38 |
39 | // or via attribute for string state
40 | undoerEl.setAttribute('state', 'new state');
41 |
42 | ```
43 |
44 | ### Imperative JavaScript
45 |
46 | You can also use the raw `Undoer` class without CEs:
47 |
48 | ```js
49 | import {Undoer} from './node_modules/undoer/undoer.js';
50 | // or
51 | import {Undoer} from 'undoer'; // your build system might allow this
52 |
53 | // construct with callback and push state
54 | const initialState = null; // default is null
55 | const undoer = new Undoer((data) => {
56 | console.info('user undo or redid', data);
57 | }, initialState);
58 | undoer.push('new state');
59 | ```
60 |
61 | ## Notes
62 |
63 | This makes sense as a Web Component as the undo behavior works by adding a hidden `
` to your page.
64 | In the WC case, this is as a child of the element: in the imperative case, it's added (by default) to `document.body`.
65 |
--------------------------------------------------------------------------------
/undoer.js:
--------------------------------------------------------------------------------
1 |
2 | export class Undoer {
3 |
4 | /**
5 | * @template T
6 | * @param {function(T)} callback to call when undo/redo occurs
7 | * @param {T=} zero the zero state for undoing everything
8 | */
9 | constructor(callback, zero=null) {
10 | this._duringUpdate = false;
11 | this._stack = [zero];
12 |
13 | // nb. Previous versions of this used `input` for browsers other than Firefox (as Firefox
14 | // _only_ supports execCommand on contentEditable)
15 | this._ctrl = document.createElement('div');
16 | this._ctrl.setAttribute('aria-hidden', 'true');
17 | this._ctrl.style.opacity = 0;
18 | this._ctrl.style.position = 'fixed';
19 | this._ctrl.style.top = '-1000px';
20 | this._ctrl.style.pointerEvents = 'none';
21 | this._ctrl.tabIndex = -1;
22 |
23 | this._ctrl.contentEditable = true;
24 | this._ctrl.textContent = '0';
25 | this._ctrl.style.visibility = 'hidden'; // hide element while not used
26 |
27 | this._ctrl.addEventListener('focus', (ev) => {
28 | // Safari needs us to wait, can't blur immediately.
29 | window.setTimeout(() => void this._ctrl.blur(), 0);
30 | });
31 | this._ctrl.addEventListener('input', (ev) => {
32 | if (!this._duringUpdate) {
33 | callback(this.data);
34 | }
35 |
36 | // clear selection, otherwise user copy gesture will copy value
37 | // nb. this _probably_ won't work inside Shadow DOM
38 | // nb. this is mitigated by the fact that we set visibility: 'hidden'
39 | const s = window.getSelection();
40 | if (s.containsNode(this._ctrl, true)) {
41 | s.removeAllRanges();
42 | }
43 | });
44 | }
45 |
46 | /**
47 | * @return {number} the current stack value
48 | */
49 | get _depth() {
50 | return +(this._ctrl.textContent) || 0;
51 | }
52 |
53 | /**
54 | * @return {T} the current data
55 | * @export
56 | */
57 | get data() {
58 | return this._stack[this._depth];
59 | }
60 |
61 | /**
62 | * Pushes a new undoable event. Adds to the browser's native undo/redo stack.
63 | *
64 | * @param {T} data the data for this undo event
65 | * @param {!Node=} parent to add to, uses document.body by default
66 | * @export
67 | */
68 | push(data, parent) {
69 | // nb. We can't remove this later: the only case we could is if the user undoes everything
70 | // and then does some _other_ action (which we can't detect).
71 | if (!this._ctrl.parentNode) {
72 | // nb. we check parentNode as this would remove contentEditable's history
73 | (parent || document.body).appendChild(this._ctrl);
74 | }
75 |
76 | const nextID = this._depth + 1;
77 | this._stack.splice(nextID, this._stack.length - nextID, data);
78 |
79 | const previousFocus = document.activeElement;
80 | try {
81 | this._duringUpdate = true;
82 | this._ctrl.style.visibility = null;
83 | this._ctrl.focus();
84 | document.execCommand('selectAll');
85 | document.execCommand('insertText', false, nextID);
86 | } finally {
87 | this._duringUpdate = false;
88 | this._ctrl.style.visibility = 'hidden';
89 | }
90 |
91 | previousFocus && previousFocus.focus();
92 | }
93 | }
94 |
--------------------------------------------------------------------------------
/LICENSE:
--------------------------------------------------------------------------------
1 | Apache License
2 | Version 2.0, January 2004
3 | http://www.apache.org/licenses/
4 |
5 | TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
6 |
7 | 1. Definitions.
8 |
9 | "License" shall mean the terms and conditions for use, reproduction,
10 | and distribution as defined by Sections 1 through 9 of this document.
11 |
12 | "Licensor" shall mean the copyright owner or entity authorized by
13 | the copyright owner that is granting the License.
14 |
15 | "Legal Entity" shall mean the union of the acting entity and all
16 | other entities that control, are controlled by, or are under common
17 | control with that entity. For the purposes of this definition,
18 | "control" means (i) the power, direct or indirect, to cause the
19 | direction or management of such entity, whether by contract or
20 | otherwise, or (ii) ownership of fifty percent (50%) or more of the
21 | outstanding shares, or (iii) beneficial ownership of such entity.
22 |
23 | "You" (or "Your") shall mean an individual or Legal Entity
24 | exercising permissions granted by this License.
25 |
26 | "Source" form shall mean the preferred form for making modifications,
27 | including but not limited to software source code, documentation
28 | source, and configuration files.
29 |
30 | "Object" form shall mean any form resulting from mechanical
31 | transformation or translation of a Source form, including but
32 | not limited to compiled object code, generated documentation,
33 | and conversions to other media types.
34 |
35 | "Work" shall mean the work of authorship, whether in Source or
36 | Object form, made available under the License, as indicated by a
37 | copyright notice that is included in or attached to the work
38 | (an example is provided in the Appendix below).
39 |
40 | "Derivative Works" shall mean any work, whether in Source or Object
41 | form, that is based on (or derived from) the Work and for which the
42 | editorial revisions, annotations, elaborations, or other modifications
43 | represent, as a whole, an original work of authorship. For the purposes
44 | of this License, Derivative Works shall not include works that remain
45 | separable from, or merely link (or bind by name) to the interfaces of,
46 | the Work and Derivative Works thereof.
47 |
48 | "Contribution" shall mean any work of authorship, including
49 | the original version of the Work and any modifications or additions
50 | to that Work or Derivative Works thereof, that is intentionally
51 | submitted to Licensor for inclusion in the Work by the copyright owner
52 | or by an individual or Legal Entity authorized to submit on behalf of
53 | the copyright owner. For the purposes of this definition, "submitted"
54 | means any form of electronic, verbal, or written communication sent
55 | to the Licensor or its representatives, including but not limited to
56 | communication on electronic mailing lists, source code control systems,
57 | and issue tracking systems that are managed by, or on behalf of, the
58 | Licensor for the purpose of discussing and improving the Work, but
59 | excluding communication that is conspicuously marked or otherwise
60 | designated in writing by the copyright owner as "Not a Contribution."
61 |
62 | "Contributor" shall mean Licensor and any individual or Legal Entity
63 | on behalf of whom a Contribution has been received by Licensor and
64 | subsequently incorporated within the Work.
65 |
66 | 2. Grant of Copyright License. Subject to the terms and conditions of
67 | this License, each Contributor hereby grants to You a perpetual,
68 | worldwide, non-exclusive, no-charge, royalty-free, irrevocable
69 | copyright license to reproduce, prepare Derivative Works of,
70 | publicly display, publicly perform, sublicense, and distribute the
71 | Work and such Derivative Works in Source or Object form.
72 |
73 | 3. Grant of Patent License. Subject to the terms and conditions of
74 | this License, each Contributor hereby grants to You a perpetual,
75 | worldwide, non-exclusive, no-charge, royalty-free, irrevocable
76 | (except as stated in this section) patent license to make, have made,
77 | use, offer to sell, sell, import, and otherwise transfer the Work,
78 | where such license applies only to those patent claims licensable
79 | by such Contributor that are necessarily infringed by their
80 | Contribution(s) alone or by combination of their Contribution(s)
81 | with the Work to which such Contribution(s) was submitted. If You
82 | institute patent litigation against any entity (including a
83 | cross-claim or counterclaim in a lawsuit) alleging that the Work
84 | or a Contribution incorporated within the Work constitutes direct
85 | or contributory patent infringement, then any patent licenses
86 | granted to You under this License for that Work shall terminate
87 | as of the date such litigation is filed.
88 |
89 | 4. Redistribution. You may reproduce and distribute copies of the
90 | Work or Derivative Works thereof in any medium, with or without
91 | modifications, and in Source or Object form, provided that You
92 | meet the following conditions:
93 |
94 | (a) You must give any other recipients of the Work or
95 | Derivative Works a copy of this License; and
96 |
97 | (b) You must cause any modified files to carry prominent notices
98 | stating that You changed the files; and
99 |
100 | (c) You must retain, in the Source form of any Derivative Works
101 | that You distribute, all copyright, patent, trademark, and
102 | attribution notices from the Source form of the Work,
103 | excluding those notices that do not pertain to any part of
104 | the Derivative Works; and
105 |
106 | (d) If the Work includes a "NOTICE" text file as part of its
107 | distribution, then any Derivative Works that You distribute must
108 | include a readable copy of the attribution notices contained
109 | within such NOTICE file, excluding those notices that do not
110 | pertain to any part of the Derivative Works, in at least one
111 | of the following places: within a NOTICE text file distributed
112 | as part of the Derivative Works; within the Source form or
113 | documentation, if provided along with the Derivative Works; or,
114 | within a display generated by the Derivative Works, if and
115 | wherever such third-party notices normally appear. The contents
116 | of the NOTICE file are for informational purposes only and
117 | do not modify the License. You may add Your own attribution
118 | notices within Derivative Works that You distribute, alongside
119 | or as an addendum to the NOTICE text from the Work, provided
120 | that such additional attribution notices cannot be construed
121 | as modifying the License.
122 |
123 | You may add Your own copyright statement to Your modifications and
124 | may provide additional or different license terms and conditions
125 | for use, reproduction, or distribution of Your modifications, or
126 | for any such Derivative Works as a whole, provided Your use,
127 | reproduction, and distribution of the Work otherwise complies with
128 | the conditions stated in this License.
129 |
130 | 5. Submission of Contributions. Unless You explicitly state otherwise,
131 | any Contribution intentionally submitted for inclusion in the Work
132 | by You to the Licensor shall be under the terms and conditions of
133 | this License, without any additional terms or conditions.
134 | Notwithstanding the above, nothing herein shall supersede or modify
135 | the terms of any separate license agreement you may have executed
136 | with Licensor regarding such Contributions.
137 |
138 | 6. Trademarks. This License does not grant permission to use the trade
139 | names, trademarks, service marks, or product names of the Licensor,
140 | except as required for reasonable and customary use in describing the
141 | origin of the Work and reproducing the content of the NOTICE file.
142 |
143 | 7. Disclaimer of Warranty. Unless required by applicable law or
144 | agreed to in writing, Licensor provides the Work (and each
145 | Contributor provides its Contributions) on an "AS IS" BASIS,
146 | WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
147 | implied, including, without limitation, any warranties or conditions
148 | of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A
149 | PARTICULAR PURPOSE. You are solely responsible for determining the
150 | appropriateness of using or redistributing the Work and assume any
151 | risks associated with Your exercise of permissions under this License.
152 |
153 | 8. Limitation of Liability. In no event and under no legal theory,
154 | whether in tort (including negligence), contract, or otherwise,
155 | unless required by applicable law (such as deliberate and grossly
156 | negligent acts) or agreed to in writing, shall any Contributor be
157 | liable to You for damages, including any direct, indirect, special,
158 | incidental, or consequential damages of any character arising as a
159 | result of this License or out of the use or inability to use the
160 | Work (including but not limited to damages for loss of goodwill,
161 | work stoppage, computer failure or malfunction, or any and all
162 | other commercial damages or losses), even if such Contributor
163 | has been advised of the possibility of such damages.
164 |
165 | 9. Accepting Warranty or Additional Liability. While redistributing
166 | the Work or Derivative Works thereof, You may choose to offer,
167 | and charge a fee for, acceptance of support, warranty, indemnity,
168 | or other liability obligations and/or rights consistent with this
169 | License. However, in accepting such obligations, You may act only
170 | on Your own behalf and on Your sole responsibility, not on behalf
171 | of any other Contributor, and only if You agree to indemnify,
172 | defend, and hold each Contributor harmless for any liability
173 | incurred by, or claims asserted against, such Contributor by reason
174 | of your accepting any such warranty or additional liability.
175 |
176 | END OF TERMS AND CONDITIONS
177 |
178 | APPENDIX: How to apply the Apache License to your work.
179 |
180 | To apply the Apache License to your work, attach the following
181 | boilerplate notice, with the fields enclosed by brackets "[]"
182 | replaced with your own identifying information. (Don't include
183 | the brackets!) The text should be enclosed in the appropriate
184 | comment syntax for the file format. We also recommend that a
185 | file or class name and description of purpose be included on the
186 | same "printed page" as the copyright notice for easier
187 | identification within third-party archives.
188 |
189 | Copyright [yyyy] [name of copyright owner]
190 |
191 | Licensed under the Apache License, Version 2.0 (the "License");
192 | you may not use this file except in compliance with the License.
193 | You may obtain a copy of the License at
194 |
195 | http://www.apache.org/licenses/LICENSE-2.0
196 |
197 | Unless required by applicable law or agreed to in writing, software
198 | distributed under the License is distributed on an "AS IS" BASIS,
199 | WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
200 | See the License for the specific language governing permissions and
201 | limitations under the License.
202 |
--------------------------------------------------------------------------------