Determine if string is in base64 using JavaScript

Question

I\'m using the window.atob(\'string\') function to decode a string from base64 to a string. Now I wonder, is there any way to check that \'string\' is actually

Answer 1

I would use a regular expression for that. Try this one:

/^([0-9a-zA-Z+/]{4})*(([0-9a-zA-Z+/]{2}==)|([0-9a-zA-Z+/]{3}=))?$/

Explanation:

^                          # Start of input
([0-9a-zA-Z+/]{4})*        # Groups of 4 valid characters decode
                           # to 24 bits of data for each group
(                          # Either ending with:
    ([0-9a-zA-Z+/]{2}==)   # two valid characters followed by ==
    |                      # , or
    ([0-9a-zA-Z+/]{3}=)    # three valid characters followed by =
)?                         # , or nothing
$                          # End of input