2018-10-10 22:03:03 +00:00
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---
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id: 587d7dbe367417b2b2512bb8
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2020-12-16 07:37:30 +00:00
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title: 使用 @if 和 @else 为你的样式添加逻辑
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2018-10-10 22:03:03 +00:00
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challengeType: 0
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2020-09-07 08:11:08 +00:00
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forumTopicId: 301463
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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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Sass 中的`@if`指令对于测试特定情况非常有用--它的工作方式与 JavaScript中的`if`语句类似。
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2020-09-07 08:11:08 +00:00
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```scss
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@mixin make-bold($bool) {
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@if $bool == true {
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font-weight: bold;
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}
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}
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```
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2020-12-16 07:37:30 +00:00
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类似 JavaScript,你可以在 Sass 中使用`@else if`和`@else`添加更多条件:
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2020-09-07 08:11:08 +00:00
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```scss
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@mixin text-effect($val) {
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@if $val == danger {
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color: red;
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}
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@else if $val == alert {
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color: yellow;
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}
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@else if $val == success {
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color: green;
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}
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@else {
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color: black;
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}
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}
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```
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2020-12-16 07:37:30 +00:00
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# --instructions--
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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创建一个名为`border-stroke`的`mixin`,它接受一个参数`$val`。`mixin`应使用`@if`,`@else if`和`@else`检查以下条件:
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2020-09-07 08:11:08 +00:00
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```scss
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light - 1px solid black
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medium - 3px solid black
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heavy - 6px solid black
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```
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2020-12-16 07:37:30 +00:00
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如果 `$val` 不是 `light`、`medium` 或者 `heavy`,border 应该设置为 `none`。
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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# --hints--
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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你应该声明一个名为`border-stroke`的`mixin`,它有一个名为`$val`的参数。
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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(code.match(/@mixin\s+?border-stroke\s*?\(\s*?\$val\s*?\)\s*?{/gi));
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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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`mixin`应该有一个`@if`语句来检查`$val`是否很轻,并将`border`设置为 1px 纯黑色。
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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```js
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assert(
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code.match(
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/@if\s+?\$val\s*?===?\s*?light\s*?{\s*?border\s*?:\s*?1px\s+?solid\s+?black\s*?;\s*?}/gi
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)
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);
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```
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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`mixin`应该有一个`@else if`语句来检查`$val`是否中等,并设置`border`为3px 纯黑色。
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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(
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code.match(
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/@else\s+?if\s+?\$val\s*?===?\s*?medium\s*?{\s*?border\s*?:\s*?3px\s+?solid\s+?black\s*?;\s*?}/gi
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)
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);
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```
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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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`mixin`应该有一个`@else if`语句来检查`$val`是否很重,并设置`border`为6px 纯黑色。
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2020-09-07 08:11:08 +00:00
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2020-12-16 07:37:30 +00:00
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```js
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assert(
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code.match(
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/@else\s+?if\s+?\$val\s*?===?\s*?heavy\s*?{\s*?border\s*?:\s*?6px\s+?solid\s+?black\s*?;\s*?}/gi
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)
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);
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```
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2020-09-07 08:11:08 +00:00
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2020-12-16 07:37:30 +00:00
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`mixin`应该有一个`@else`语句来将`border`设置为 none。
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2020-09-07 08:11:08 +00:00
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2020-12-16 07:37:30 +00:00
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```js
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assert(code.match(/@else\s*?{\s*?border\s*?:\s*?none\s*?;\s*?}/gi));
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2018-10-10 22:03:03 +00:00
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```
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2020-08-13 15:24:35 +00:00
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2020-12-16 07:37:30 +00:00
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# --solutions--
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