How to replace a substring between two indices

Question

I want to replace text between two indices in Javascript, something like:

str = "The Hello World Code!"; str.replaceBetween(4,9,"Hi"); // outputs "The Hi World Code" 

The indices and the string are both dynamic.

How could I go about doing this?

Answer 1

There is no such method in JavaScript. But you can always create your own:

String.prototype.replaceBetween = function(start, end, what) {    return this.substring(0, start) + what + this.substring(end);  };    console.log("The Hello World Code!".replaceBetween(4, 9, "Hi"));

Answer 2

The accepted answer is correct, but I wanted to avoid extending the String prototype:

function replaceBetween(origin, startIndex, endIndex, insertion) {   return origin.substring(0, startIndex) + insertion + origin.substring(endIndex); } 

Usage:

replaceBetween('Hi World', 3, 7, 'People');  // Hi People 

If using a concise arrow function, then it's:

const replaceBetween = (origin, startIndex, endIndex, insertion) =>   origin.substring(0, startIndex) + insertion + origin.substring(endIndex); 

If using template literals, then it's:

const replaceBetween = (origin, startIndex, endIndex, insertion) =>   `${origin.substring(0, startIndex)}${insertion}${origin.substring(endIndex)}`;