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Some systems like thistle uses a variant of base 64 encoding that is safe for URL encoding, this differs from standard base 64 encoding in that there is no padding ‘=’ used and the ‘+’ and ‘/’ characters are replaced by ‘- and ‘_’ see http://en.wikipedia.org/wiki/Base64 for details if required.

Encode & Decode base64 data value with Javascript in Client Action for encode value (text,number,etc), encode input parameter  value, local variable value, client variable value.