Lua Programming/How to Lua/symbols/hash

Length operator

The hash symbol acts as a unary length operator.

Length of a string

When used against a string, the length operator returns the number of bytes within the string.

Length of a table

When used against atable that is not sparse, the length operator returns the number of the last non null element in the table. For an empty table, a value of zero will be returned:

Sparse tables

Note that if a table contains holes, the length operator considers the first null element to be the end of the table, and will return the element number that immediately precedes the null element.