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What is the difference between String#slice(), String#substring(), String#substr() ?

The 3 methods are used to extract a portion of a String. They differ in the interpretation of their two parameters. In every case they return a new string.

String.prototype.slice(begin[, end]) slices the String from begin to (not included) end.

  • if begin or end are negatives, the value is considered as starting from the end of the string.
  • if end is greater than or equal to begin, an empty string is returned.
> 'abcde'.slice(0, 4)
'abcd'

> 'abcde'.slice(-3, 4)
'cd'

> 'abcde'.slice(1,1)
''

> 'abcde'.slice(2,1)
''

> 'abcde'.slice()
'abcde'

String.prototype.substring(begin[, end]) returns a subset of the String between begin to (not included) end.

  • negative or NaN values are treated as 0.
  • if end is greater than or equal to begin, it is as if the two arguments were swapped (i.e 'abcd'.subtring(2,1) === 'abc'.substring(1,2)).
> 'abcde'.substring(0, 4)
'abcd'

> 'abcde'.substring(-3, 4)
'abcd'

> 'abcde'.substring(1,1)
''

> 'abcde'.substring(2,1)
'b'

> 'abcde'.substring()
'abcde'

String.prototype.substr(start[, length]) returns the character in a string starting at start, with the given length.

  • if start is negative, the value is considered as starting from the end of the string.
> 'abcde'.substr(0, 4)
'abcd'

> 'abcde'.substr(-3, 4)
'cde'

> 'abcde'.substr(1,1)
'b'

> 'abcde'.substr(2,1)
'c'

> 'abcde'.substr()
'abcde'

See MDN - String.prototype.slice() See MDN - String.prototype.substring() See MDN - String.prototype.substr()