ee1e8abd87
* feat(tools): add seed/solution restore script * chore(curriculum): remove empty sections' markers * chore(curriculum): add seed + solution to Chinese * chore: remove old formatter * fix: update getChallenges parse translated challenges separately, without reference to the source * chore(curriculum): add dashedName to English * chore(curriculum): add dashedName to Chinese * refactor: remove unused challenge property 'name' * fix: relax dashedName requirement * fix: stray tag Remove stray `pre` tag from challenge file. Signed-off-by: nhcarrigan <nhcarrigan@gmail.com> Co-authored-by: nhcarrigan <nhcarrigan@gmail.com>
158 lines
2.5 KiB
Markdown
158 lines
2.5 KiB
Markdown
---
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id: 56533eb9ac21ba0edf2244e0
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title: 用一个 Switch 语句来替代多个 if else 语句
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challengeType: 1
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videoUrl: 'https://scrimba.com/c/c3JE8fy'
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forumTopicId: 18266
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dashedName: replacing-if-else-chains-with-switch
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---
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# --description--
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如果你有多个选项需要选择，`switch`语句写起来会比多个串联的`if`/`if else`语句容易些，譬如:
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```js
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if (val === 1) {
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answer = "a";
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} else if (val === 2) {
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answer = "b";
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} else {
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answer = "c";
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}
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```
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可以被下面替代：
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```js
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switch(val) {
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case 1:
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answer = "a";
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break;
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case 2:
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answer = "b";
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break;
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default:
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answer = "c";
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}
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```
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# --instructions--
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把串联的`if`/`if else`语句改成`switch`语句。
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# --hints--
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不要使用`else`表达式。
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```js
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assert(!/else/g.test(code));
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```
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不要使用`if`表达式。
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```js
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assert(!/if/g.test(code));
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```
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你应该有至少 4 个`break`表达式。
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```js
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assert(code.match(/break/g).length >= 4);
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```
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`chainToSwitch("bob")`应该为 "Marley"。
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```js
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assert(chainToSwitch('bob') === 'Marley');
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```
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`chainToSwitch(42)`应该为 "The Answer"。
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```js
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assert(chainToSwitch(42) === 'The Answer');
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```
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`chainToSwitch(1)`应该为 "There is no
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```js
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assert(chainToSwitch(1) === 'There is no #1');
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```
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`chainToSwitch(99)`应该为 "Missed me by this much!"。
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```js
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assert(chainToSwitch(99) === 'Missed me by this much!');
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```
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`chainToSwitch(7)`应该为 "Ate Nine"。
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```js
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assert(chainToSwitch(7) === 'Ate Nine');
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```
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`chainToSwitch("John")`应该为 "" (empty string)。
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```js
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assert(chainToSwitch('John') === '');
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```
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`chainToSwitch(156)`应该为 "" (empty string)。
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```js
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assert(chainToSwitch(156) === '');
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```
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# --seed--
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## --seed-contents--
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```js
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function chainToSwitch(val) {
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var answer = "";
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// Only change code below this line
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if (val === "bob") {
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answer = "Marley";
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} else if (val === 42) {
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answer = "The Answer";
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} else if (val === 1) {
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answer = "There is no #1";
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} else if (val === 99) {
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answer = "Missed me by this much!";
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} else if (val === 7) {
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answer = "Ate Nine";
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}
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// Only change code above this line
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return answer;
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}
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chainToSwitch(7);
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```
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# --solutions--
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```js
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function chainToSwitch(val) {
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var answer = "";
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switch(val) {
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case "bob":
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answer = "Marley";
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break;
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case 42:
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answer = "The Answer";
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break;
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case 1:
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answer = "There is no #1";
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break;
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case 99:
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answer = "Missed me by this much!";
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break;
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case 7:
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answer = "Ate Nine";
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}
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return answer;
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}
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```
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