How to Count Character Occurrences and Validate String Length in JavaScript?

Counting Character Occurrences and Validating String Length in Javascript

In various programming scenarios, it often becomes necessary to count the number of times a character appears within a given string. Additionally, validating the length of individual strings after splitting can ensure data integrity.

Approach:

To tackle this problem in Javascript, we can utilize the match() method in conjunction with regular expressions. This approach allows us to determine the count of specific characters or substrings quickly and efficiently.

Character Occurrence Count:

To count the occurrences of a particular character, we can create a regular expression using the following syntax:

myRegularExpression = new RegExp("targetCharacter", "g");

For instance, if we want to count the number of commas in the string, we can use the following regular expression:

myRegularExpression = new RegExp(",", "g");

Once we have created the regular expression, we can use the match() method to obtain an array of all matching occurrences in the string. The match() method returns null if no match is found, and the length of the array represents the number of occurrences.

count = (myString.match(myRegularExpression) || []).length;

String Length Validation:

To validate the length of each string after splitting, we can use a similar approach. We can create a regular expression to match any string that exceeds the specified maximum length and then test each substring against it:

myRegularExpression = new RegExp(".{15,}", "g");

The above regular expression matches any string that contains 15 or more characters in a row. Using the match() method, we can obtain an array of all matching substrings:

invalidStrings = (myString.match(myRegularExpression) || []);

If the length of invalidStrings is greater than 0, it signifies that there are strings exceeding the specified maximum length.

Example:

Consider the string:

mainStr = "str1,str2,str3,str4";

To count the number of commas:

count = (mainStr.match(/,/g) || []).length;

To validate string length (assuming a maximum length of 15 characters):

myRegularExpression = new RegExp(".{15,}", "g");
invalidStrings = (mainStr.match(myRegularExpression) || []);

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