🔪stringKnife.js

function stringKnife(str, range, remove = false) {
  if (typeof range == "number") range = [range, undefined];
  const [start, end] = range;
  const sliced = str.slice(start, end);
  if ((!remove && !end && start > 0) || (remove && start < 0))
    return str.replace(sliced, "");
  return sliced;
}

// Usage
// let myString = "Hello World3"
// 1. get string from the start : stringKnife(myString, 2) 👉 He
// 2. get string from the back : stringKnife(myString, -3) 👉 ld3
// 3. get string from using range : stringKnife(myString, [6, 11]) 👉 World
// 4. remove string from the start : stringKnife(myString, 2, true) 👉 llo World3
// 5. remove string from the back : stringKnife(myString, -2, true) 👉 Hello Worl

// A simplified version 
// function stringKnife(str, range, remove = false) {
//   let sliced = str.slice(range);
//   if ((!remove && range > 0) || (remove && range < 0))
//     return str.replace(sliced, "");
//   return sliced;
// }