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

Iterate less the second time (just when first letter of substring matches) but still uses 2 for loops:

   function findSubstringOccurrences(str, word) {        let occurrences = 0;        for(let i=0; i<str.length; i++){            if(word[0] === str[i]){ // to make it faster and iterate less                for(let j=0; j<word.length; j++){                    if(str[i+j] !== word[j]) break;                    if(j === word.length - 1) occurrences++;                }            }        }        return occurrences;    }    console.log(findSubstringOccurrences("jdlfkfomgkdjfomglo", "omg"));