What is the difference between substr and substring?

What is the difference between

alert("abc".substr(0,2));

and

alert("abc".substring(0,2));

They both seem to output “ab”.

The difference is in the second argument. The second argument to substring is the index to stop at (but not include), but the second argument to substr is the maximum length to return.

Links?

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/substr

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/substring

substr (MDN) takes parameters as (from, length).
substring (MDN) takes parameters as (from, to).

Update: MDN considers substr legacy.

alert("abc".substr(1,2)); // returns "bc"
alert("abc".substring(1,2)); // returns "b"

You can remember substring (with an i) takes indices, as does yet another string extraction method, slice (with an i).

When starting from 0 you can use either method.