Substrings

substring is used to take a part of a string.
Syntax: substring(first_index,last_index).

var a = 'Hello world!';
document.write(a.substring(1,6));

The preceding code snippet gives 'ello ' . Note that the ‘w’ (index 6) is not part of this substring.

We could also do,

var a = 'Hello world!';
document.write(a.substring(2));

This gives the whole string from the character with index 2. 'llo world!'

substr

There is also a method substr() that works slightly differently. Instead of the second number being an index number,
it gives the number of characters.

var a = 'Hello world!';
document.write(a.substr(1,6));

starts at the character with index 1 (‘e’) and then gives 6 characters, so the output is ello w