Javascript: substr() v.s. substring()

substr() method extracts a specified number of characters in a string, from a start index.

Syntax: string.substr(start, length);

substring() method extracts the chars in a string between two specified indexes.

Syntax: string.substring(start, stop);

Quick Notes aout Substr:

• If start is negative, Internet Explorer returns the whole string. That’s wrong! IE should use the last character in the string.

Quick Notes about Substring:

• If start equals stop, it returns an empty string.
• If stop is omitted, it extracts characters to the end of the string.
• If either argument is less than 0 or is NaN, it is treated as if it were 0.
• If either argument is greater than string’s length, either argument will use string’s length.
• If start > stop, then substring will swap those 2 arguments.

UPDATE (Added Slice upon request)

slice() works like substring() with a few different behaviors.

Syntax: string.slice(start, stop);

Quick Notes about Slice:

• If stop is omitted, slice extracted chars to the end of the string, exactly like substring().
• If start > stop, slice() will NOT swap the 2 arguments.
• If start is negative, slice() will set char from the end of string, exactly like substr() in Firefox. This behavior is observed in both Firefox and IE.
• If stop is negative, slice() will set stop to: (string.length – 1) – stop (original value).

References:

• Mozilla Developer Documentation – substr()
• Mozilla Developer Documentation – substring()
• Mozilla Developer Documentation – slice()
• MSDN Documentation – substr()
• MSDN Documentation – substring()
• MSDN Documentation – slice()
• Opera ECMAScript &/ Javascript Support (including Opera for Wii)