Count number of occurrences of a character in a string in JavaScript

This post will discuss how to count the total number of occurrences of a character in a string with JavaScript.

1. Using Regex

Regular expressions are often used in JavaScript for matching a text with a pattern. The following code example demonstrates its usage to get the count of the characters in the string. It uses the match() method of the string instance.

var str = "A,B,C,D,E";

var count = (str.match(/\,/g) || []).length;

console.log(count);

Output: 4

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The match() method returns null if there were no matches. To avoid calling the length property on the null value, we have used the logical OR operator [].

2. Using `String.prototype.split()` function

Here, the idea is to split the string using the given character as a delimiter and determine the count using the resulting array’s length. This can be easily done using the split() method:

var str = "A,B,C,D,E";

var ch = ',';

var count = str.split(ch).length - 1;

console.log(count);

Output: 4

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3. Using `Array.prototype.filter()` function

Another alternative is to filter the array to allow only those values matching the given character. This would translate to a simple code below:

var str = "A,B,C,D,E";

var ch = ',';

var count = [...str].filter(x => x === ch).length;

console.log(count);

Output: 4

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4. Using Underscore/Lodash Library

If you prefer Underscore or Lodash library, you can use the _.countBy method. It basically groups characters of the array and returns counts for each character. You can use it as:

var _ = require('lodash'); // or underscore.js

var str = "A,B,C,D,E";

var ch = ',';

var count = _.countBy(str)[ch];

console.log(count);

Output: 4

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That’s all about counting the number of occurrences of a character in a string in JavaScript.

Count number of occurrences of a character in a string in JavaScript

1. Using Regex

2. Using String.prototype.split() function

3. Using Array.prototype.filter() function

4. Using Underscore/Lodash Library

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2. Using `String.prototype.split()` function

3. Using `Array.prototype.filter()` function