Step by Step solution about How to resolve the algorithm Count occurrences of a substring step by step in the JavaScript programming language

First Function: countSubstring

• Input: Two strings: str (the original string) and subStr (the substring to search for).
• Output: The number of occurrences of subStr within str.

Implementation Details:

1. It uses the match method of the str string with a regular expression (regex) to find all occurrences of subStr. The regex is constructed using new RegExp(subStr, "g"), where "g" indicates that the regular expression should perform a global search (i.e., find all matches).
2. The result of match is an array of matches, or null if no matches are found.
3. If matches is not null, it returns the length of the matches array, which is equal to the number of occurrences of subStr in str. Otherwise, it returns 0.

Second Function: countSubString

• Input: Two strings: str (the original string) and subStr (the substring to search for).
• Output: The number of occurrences of subStr within str.

Implementation Details:

1. It uses the split method of the str string with subStr as the separator. This splits the str string into an array of substrings at each occurrence of subStr.
2. It subtracts 1 from the length of the resulting array because the first element of the array will be the entire original string, which does not count as an occurrence of subStr.
3. The result is the number of occurrences of subStr in str.

Comparison:

Both functions perform the same task: counting the number of occurrences of a substring within a string. However, they use different approaches:

• countSubstring uses regular expressions, which are more flexible and can be used to find more complex patterns.
• countSubString uses the split method, which is simpler and more efficient for finding simple substrings.

Which function is better depends on the specific requirements and performance considerations of the application.

function countSubstring(str, subStr) {
    var matches = str.match(new RegExp(subStr, "g"));
    return matches ? matches.length : 0;
}


const countSubString = (str, subStr) => str.split(subStr).length - 1;