freeCodeCamp/curriculum/challenges/english/08-coding-interview-prep/rosetta-code/balanced-brackets.english.md

---
title: Balanced brackets
id: 594dc6c729e5700999302b45
challengeType: 5
---

## Description
<section id='description'>
<p>Determine whether a generated string of brackets is balanced; that is, whether it consists entirely of pairs of opening/closing brackets (in that order), none of which mis-nest.</p>
Examples:
<p class='rosetta__paragraph'>(empty) true</p>
<p class='rosetta__paragraph'><code>[]</code> true</p>
<p class='rosetta__paragraph'><code>][</code> false</p>
<p class='rosetta__paragraph'><code>[][]</code> true</p>
<p class='rosetta__paragraph'><code>][][</code> false</p>
<p class='rosetta__paragraph'><code>[]][[]</code> false</p>
<p class='rosetta__paragraph'><code>[[[[]]]]</code> true</p>
</section>

## Instructions
<section id='instructions'>

</section>

## Tests
<section id='tests'>

```yml
tests:
  - text: <code>isBalanced</code> is a function.
    testString: 'assert(typeof isBalanced === ''function'', ''<code>isBalanced</code> is a function.'');'
  - text: '<code>isBalanced("[]")</code> should return true.'
    testString: 'assert(isBalanced(testCases[0]), ''<code>isBalanced("[]")</code> should return true.'');'
  - text: '<code>isBalanced("]][[[][][][]][")</code> should return false.'
    testString: 'assert(!isBalanced(testCases[1]), ''<code>isBalanced("]][[[][][][]][")</code> should return false.'');'
  - text: '<code>isBalanced("[][[[[][][[[]]]]]]")</code> should return true.'
    testString: 'assert(isBalanced(testCases[2]), ''<code>isBalanced("[][[[[][][[[]]]]]]")</code> should return true.'');'
  - text: '<code>isBalanced("][")</code> should return true.'
    testString: 'assert(!isBalanced(testCases[3]), ''<code>isBalanced("][")</code> should return true.'');'
  - text: '<code>isBalanced("[[[]]]][[]")</code> should return true.'
    testString: 'assert(!isBalanced(testCases[4]), ''<code>isBalanced("[[[]]]][[]")</code> should return true.'');'
  - text: '<code>isBalanced("][[]")</code> should return true.'
    testString: 'assert(!isBalanced(testCases[5]), ''<code>isBalanced("][[]")</code> should return true.'');'
  - text: '<code>isBalanced("][[][]][[[]]")</code> should return true.'
    testString: 'assert(!isBalanced(testCases[6]), ''<code>isBalanced("][[][]][[[]]")</code> should return true.'');'
  - text: '<code>isBalanced("[[][]]][")</code> should return true.'
    testString: 'assert(!isBalanced(testCases[7]), ''<code>isBalanced("[[][]]][")</code> should return true.'');'
  - text: '<code>isBalanced("[[[]]][[]]]][][[")</code> should return true.'
    testString: 'assert(!isBalanced(testCases[8]), ''<code>isBalanced("[[[]]][[]]]][][[")</code> should return true.'');'
  - text: '<code>isBalanced("[]][[]]][[[[][]]")</code> should return true.'
    testString: 'assert(!isBalanced(testCases[9]), ''<code>isBalanced("[]][[]]][[[[][]]")</code> should return true.'');'
  - text: '<code>isBalanced("][]][[][")</code> should return true.'
    testString: 'assert(!isBalanced(testCases[10]), ''<code>isBalanced("][]][[][")</code> should return true.'');'
  - text: '<code>isBalanced("[[]][[][]]")</code> should return true.'
    testString: 'assert(isBalanced(testCases[11]), ''<code>isBalanced("[[]][[][]]")</code> should return true.'');'
  - text: '<code>isBalanced("[[]]")</code> should return true.'
    testString: 'assert(isBalanced(testCases[12]), ''<code>isBalanced("[[]]")</code> should return true.'');'
  - text: '<code>isBalanced("]][]][[]][[[")</code> should return true.'
    testString: 'assert(!isBalanced(testCases[13]), ''<code>isBalanced("]][]][[]][[[")</code> should return true.'');'
  - text: '<code>isBalanced("][]][][[")</code> should return true.'
    testString: 'assert(!isBalanced(testCases[14]), ''<code>isBalanced("][]][][[")</code> should return true.'');'
  - text: '<code>isBalanced("][][")</code> should return true.'
    testString: 'assert(!isBalanced(testCases[15]), ''<code>isBalanced("][][")</code> should return true.'');'
  - text: '<code>isBalanced("[[]]][][][[]][")</code> should return true.'
    testString: 'assert(!isBalanced(testCases[16]), ''<code>isBalanced("[[]]][][][[]][")</code> should return true.'');'
  - text: <code>isBalanced("")</code> should return true.
    testString: 'assert(isBalanced(testCases[17]), ''<code>isBalanced("")</code> should return true.'');'

```

</section>

## Challenge Seed
<section id='challengeSeed'>

<div id='js-seed'>

```js
function isBalanced (str) {
  // Good luck!
  return true;
}
```

</div>


### After Test
<div id='js-teardown'>

```js
console.info('after the test');
```

</div>

</section>

## Solution
<section id='solution'>


```js
function isBalanced (str) {
  if (str === '') return true;
  let a = str;
  let b;
  do {
    b = a;
    a = a.replace(/\[\]/g, '');
  } while (a !== b);
  return !a;
}

```

</section>