86 lines
2.0 KiB
Markdown
86 lines
2.0 KiB
Markdown
---
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title: Count occurrences of a substring
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id: 596fda99c69f779975a1b67d
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challengeType: 5
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forumTopicId: 302237
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---
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## Description
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<section id='description'>
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Create a function, or show a built-in function, to count the number of non-overlapping occurrences of a substring inside a string.
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The function should take two arguments:
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<ul>
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<li>the first argument being the string to search, and</li>
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<li>the second a substring to be searched for.</li>
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</ul>
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It should return an integer count.
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The matching should yield the highest number of non-overlapping matches.
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In general, this essentially means matching from left-to-right or right-to-left.
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</section>
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## Instructions
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<section id='instructions'>
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</section>
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## Tests
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<section id='tests'>
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```yml
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tests:
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- text: <code>countSubstring</code> is a function.
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testString: assert(typeof countSubstring === 'function');
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- text: <code>countSubstring("the three truths", "th")</code> should return <code>3</code>.
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testString: assert.equal(countSubstring(testCases[0], searchString[0]), results[0]);
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- text: <code>countSubstring("ababababab", "abab")</code> should return <code>2</code>.
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testString: assert.equal(countSubstring(testCases[1], searchString[1]), results[1]);
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- text: <code>countSubstring("abaabba*bbaba*bbab", "a*b")</code> should return <code>2</code>.
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testString: assert.equal(countSubstring(testCases[2], searchString[2]), results[2]);
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```
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</section>
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## Challenge Seed
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<section id='challengeSeed'>
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<div id='js-seed'>
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```js
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function countSubstring(str, subStr) {
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// Good luck!
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return true;
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}
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```
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</div>
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### After Test
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<div id='js-teardown'>
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```js
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const testCases = ['the three truths', 'ababababab', 'abaabba*bbaba*bbab'];
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const searchString = ['th', 'abab', 'a*b'];
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const results = [3, 2, 2];
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```
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</div>
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</section>
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## Solution
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<section id='solution'>
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```js
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function countSubstring(str, subStr) {
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const escapedSubStr = subStr.replace(/[.+*?^$[\]{}()|/]/g, '\\$&');
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const matches = str.match(new RegExp(escapedSubStr, 'g'));
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return matches ? matches.length : 0;
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}
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```
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</section>
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