2018-10-10 22:03:03 +00:00
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id: 587d7790367417b2b2512ab0
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2020-12-16 07:37:30 +00:00
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title: 使用 tabindex 将键盘焦点添加到元素中
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2018-10-10 22:03:03 +00:00
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challengeType: 0
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2020-02-11 09:06:41 +00:00
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videoUrl: 'https://scrimba.com/c/cmzMDHW'
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forumTopicId: 301027
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2021-01-13 02:31:00 +00:00
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dashedName: use-tabindex-to-add-keyboard-focus-to-an-element
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2018-10-10 22:03:03 +00:00
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---
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2020-12-16 07:37:30 +00:00
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# --description--
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2018-10-10 22:03:03 +00:00
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2021-03-05 15:43:24 +00:00
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HTML 的 `tabindex` 属性有三种与标签焦点相关的功能。 当它在一个元素上时，表示该元素可以获得焦点。 tabindex 的值（可以是零、负整数或正整数）定义了行为。
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2018-10-10 22:03:03 +00:00
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2021-02-06 04:42:36 +00:00
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当用户使用键盘浏览页面时，诸如链接、表单控件等元素可以自动获得焦点。 它们获得焦点的顺序与它们出现在 HTML 文档流中的顺序一致。 我们可以通过将其他标签（如 `div`、`span`、`p` 等）的 `tabindex` 属性值设为 0 来让它们实现类似的效果。 比如：
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2018-10-10 22:03:03 +00:00
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2021-03-20 15:47:30 +00:00
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```html
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<div tabindex="0">I need keyboard focus!</div>
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```
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2018-10-10 22:03:03 +00:00
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2021-02-06 04:42:36 +00:00
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**注意：** `tabindex` 属性值为负整数（通常为 -1）的标签也是可以获得焦点的，只是不可以通过键盘操作（如 tab 键）来获得焦点。 这种方法通常用于以编程的方式使内容获得焦点（如：将焦点设置到用 `div` 实现的弹出框上）的场景。 只是这部分内容已经超出了当前挑战的范围。
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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# --instructions--
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2018-10-10 22:03:03 +00:00
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2021-03-20 15:47:30 +00:00
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Camper Cat 新建了一个用来收集他的用户信息的调查。 他知道输入框可以自动获得键盘焦点，但他希望用户使用键盘切换标签时，焦点可以停留在指示文字（Instructions）上。 请给 `p` 标签添加一个 `tabindex` 属性，将属性值设置为 `0`。 注意：使用 `tabindex` 属性还可以让 CSS 伪类 `:focus` 在 `p` 标签上生效。
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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# --hints--
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2018-10-10 22:03:03 +00:00
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2021-01-08 19:20:48 +00:00
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表单中，作为指示文字（Instructions）的 `p` 标签应具有 `tabindex` 属性。
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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```js
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assert($('p').attr('tabindex'));
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```
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2018-10-10 22:03:03 +00:00
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2021-01-08 19:20:48 +00:00
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`p` 标签的 `tabindex` 属性值应设置为 0。
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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```js
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assert($('p').attr('tabindex') == '0');
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2018-10-10 22:03:03 +00:00
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```
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2020-02-11 09:06:41 +00:00
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2021-01-13 02:31:00 +00:00
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# --seed--
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## --seed-contents--
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```html
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<head>
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<style>
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p:focus {
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background-color: yellow;
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}
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</style>
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</head>
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<body>
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<header>
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<h1>Ninja Survey</h1>
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</header>
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<section>
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<form>
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<p>Instructions: Fill in ALL your information then click <b>Submit</b></p>
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<label for="username">Username:</label>
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<input type="text" id="username" name="username"><br>
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<fieldset>
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<legend>What level ninja are you?</legend>
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<input id="newbie" type="radio" name="levels" value="newbie">
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<label for="newbie">Newbie Kitten</label><br>
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<input id="intermediate" type="radio" name="levels" value="intermediate">
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<label for="intermediate">Developing Student</label><br>
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<input id="master" type="radio" name="levels" value="master">
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<label for="master">9th Life Master</label>
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</fieldset>
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<br>
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<fieldset>
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<legend>Select your favorite weapons:</legend>
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<input id="stars" type="checkbox" name="weapons" value="stars">
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<label for="stars">Throwing Stars</label><br>
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<input id="nunchucks" type="checkbox" name="weapons" value="nunchucks">
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<label for="nunchucks">Nunchucks</label><br>
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<input id="sai" type="checkbox" name="weapons" value="sai">
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<label for="sai">Sai Set</label><br>
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<input id="sword" type="checkbox" name="weapons" value="sword">
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<label for="sword">Sword</label>
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</fieldset>
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<br>
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<input type="submit" name="submit" value="Submit">
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</form><br>
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</section>
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<footer>© 2018 Camper Cat</footer>
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</body>
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```
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2020-12-16 07:37:30 +00:00
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# --solutions--
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2021-01-13 02:31:00 +00:00
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```html
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<head>
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<style>
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p:focus {
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background-color: yellow;
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}
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</style>
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</head>
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<body>
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<header>
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<h1>Ninja Survey</h1>
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</header>
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<section>
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<form>
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<p tabindex="0">Instructions: Fill in ALL your information then click <b>Submit</b></p>
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<label for="username">Username:</label>
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<input type="text" id="username" name="username"><br>
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<fieldset>
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<legend>What level ninja are you?</legend>
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<input id="newbie" type="radio" name="levels" value="newbie">
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<label for="newbie">Newbie Kitten</label><br>
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<input id="intermediate" type="radio" name="levels" value="intermediate">
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<label for="intermediate">Developing Student</label><br>
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<input id="master" type="radio" name="levels" value="master">
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<label for="master">9th Life Master</label>
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</fieldset>
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<br>
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<fieldset>
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<legend>Select your favorite weapons:</legend>
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<input id="stars" type="checkbox" name="weapons" value="stars">
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<label for="stars">Throwing Stars</label><br>
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<input id="nunchucks" type="checkbox" name="weapons" value="nunchucks">
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<label for="nunchucks">Nunchucks</label><br>
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<input id="sai" type="checkbox" name="weapons" value="sai">
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<label for="sai">Sai Set</label><br>
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<input id="sword" type="checkbox" name="weapons" value="sword">
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<label for="sword">Sword</label>
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</fieldset>
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<br>
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<input type="submit" name="submit" value="Submit">
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</form><br>
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</section>
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<footer>© 2018 Camper Cat</footer>
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</body>
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```
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