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substr vs substring

Written byPhuoc Nguyen
15 Jul, 2020
Both `substr` and `substring` are common functions to get a sub-string of a given string.


  1. Both methods have two parameters. The first parameters indicate the index of starting position of sub-string. The second parameters are different.
    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`:
    'helloworld'.substr(2, 4); // 'llow'
    'helloworld'.substring(2, 4); // 'll'
  2. `substr` allows to use a negative number for the start position parameter.
    'helloworld'.substr(-2, 4); // 'ld'
    `substring`, on the other hand, will turn a negative start position to 0 (zero):
    'helloworld'.substring(-2, 5); // 'hello'
    'helloworld'.substring(0, 5); // 'hello'

Good to know

`slice` is another function for getting a sub-string. It's not deprecated as substr, and supports negative indices.
'helloworld'.slice(2, 4); // 'll'
'helloworld'.slice(-10, 5); // 'hello'
'helloworld'.slice(-5); // 'world'

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