What is the difference between slice(), substring(), and substr() functions in JavaScript?

The slice(), substring(), and substr() are all string methods in JavaScript that return a new string from a specified index. However, they have some differences in their functionality:

1. slice() method:

   • It extracts a section of a string and returns it as a new string.
   • It takes 2 parameters: the beginning index (inclusive) and the end index (exclusive). If the end index is not specified, it extracts till the end of the string.
   • It can accept negative indexes, where -1 is the last index, -2 is the second last, and so on.

2. substring() method:

   • It is similar to slice(). However, it cannot accept negative indexes.
   • If the second parameter is smaller than the first one, this method will swap the parameters. For example, str.substring(1, 0) is the same as str.substring(0, 1).

3. substr() method:

   • It is different from the above methods. The first parameter is the starting index and the second parameter is the length of the extracted part.
   • If the first parameter is negative, it counts from the end of the string.
   • Note: This method is considered a legacy function and should be avoided when possible. It's not a part of the core JavaScript language and may not be implemented in all browsers.