var string1 = "HelloWorld";
var string2 = "Work";

var fn = function( string1, string2, matchChars ) {
   return !!string2.split("").find( function(item, index){
       if (index + matchChars <= string2.length )
       {
          return string1.includes( string2.substring( index, index +  matchChars ) ); //check after each turn if the substring from index is included in string1 or not
       }
       return false;
   });
}

console.log( fn("HelloWorld", "Work", 3) );

(w{3}).+(1)