Request to improve between

[LeeeRoux]

I request to improve between
It should get all the values between left and right and return an Array of them
null incase there was no any values

/*S.prototype.between*/
function(qu1 = '"', qu2 = qu1) {
 var toReturn = [], f = false, str = this.s || this;
 for (var i = 0; i < str.length; i++) { 
  if (str.indexOf(qu1) > -1 && !f) { f = true; str = str.slice(str.indexOf(qu1) + qu1.length); };
  if (str.indexOf(qu2) > -1 && f) { 
   var value = str.substring(0, str.indexOf(qu2))
    str = str.slice(str.indexOf(qu2) + qu2.length);
    toReturn.push(value);
    f = false;
  }
 };
return toReturn.length ? toReturn : null;
}

Tested and works correctly

 "`Hello``World`".between("`");
//["Hello", "World"]

Please add it, Thankyou!