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>
64 lines
2.1 KiB
Markdown
64 lines
2.1 KiB
Markdown
---
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id: 587d7b86367417b2b2512b3d
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title: Prevent Infinite Loops with a Valid Terminal Condition
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challengeType: 1
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forumTopicId: 301192
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dashedName: prevent-infinite-loops-with-a-valid-terminal-condition
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---
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# --description--
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The final topic is the dreaded infinite loop. Loops are great tools when you need your program to run a code block a certain number of times or until a condition is met, but they need a terminal condition that ends the looping. Infinite loops are likely to freeze or crash the browser, and cause general program execution mayhem, which no one wants.
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There was an example of an infinite loop in the introduction to this section - it had no terminal condition to break out of the `while` loop inside `loopy()`. Do NOT call this function!
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```js
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function loopy() {
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while(true) {
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console.log("Hello, world!");
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}
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}
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```
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It's the programmer's job to ensure that the terminal condition, which tells the program when to break out of the loop code, is eventually reached. One error is incrementing or decrementing a counter variable in the wrong direction from the terminal condition. Another one is accidentally resetting a counter or index variable within the loop code, instead of incrementing or decrementing it.
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# --instructions--
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The `myFunc()` function contains an infinite loop because the terminal condition `i != 4` will never evaluate to `false` (and break the looping) - `i` will increment by 2 each pass, and jump right over 4 since `i` is odd to start. Fix the comparison operator in the terminal condition so the loop only runs for `i` less than or equal to 4.
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# --hints--
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Your code should change the comparison operator in the terminal condition (the middle part) of the `for` loop.
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```js
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assert(code.match(/i\s*?<=\s*?4;/g).length == 1);
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```
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Your code should fix the comparison operator in the terminal condition of the loop.
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```js
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assert(!code.match(/i\s*?!=\s*?4;/g));
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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 myFunc() {
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for (let i = 1; i != 4; i += 2) {
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console.log("Still going!");
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}
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}
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```
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# --solutions--
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```js
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function myFunc() {
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for (let i = 1; i <= 4; i += 2) {
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console.log("Still going!");
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}
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}
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```
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