substr vs substring

#Differences

1. Both methods have two parameters. The first parameters indicate the index of starting position of sub-string. The second parameters are different.
   js

   substr(startPosition, length);
   substring(startPosition, endPosition);

   As you can see, the second parameters of `substr` and `substring` are the length and the end position of sub-string respectively. Given a string of `helloworld`:
   js

   'helloworld'.substr(2, 4); // 'llow'
   'helloworld'.substring(2, 4); // 'll'

2. `substr` allows to use a negative number for the start position parameter.
   js

   'helloworld'.substr(-2, 4); // 'ld'

   `substring`, on the other hand, will turn a negative start position to 0 (zero):
   js

   'helloworld'.substring(-2, 5); // 'hello'
   'helloworld'.substring(0, 5); // 'hello'

#Good to know

'helloworld'.slice(2, 4); // 'll'
'helloworld'.slice(-10, 5); // 'hello'
'helloworld'.slice(-5); // 'world'