Answer by dimButTries for How to count string occurrence in string?

ES2020 offers a new MatchAll which might be of use in this particular context.

Here we create a new RegExp, please ensure you pass 'g' into the function.

Convert the result using Array.from and count the length, which returns 2 as per the original requestor's desired output.

let strToCheck = RegExp('is', 'g')let matchesReg = "This is a string.".matchAll(strToCheck)console.log(Array.from(matchesReg).length) // 2