JavaScript with Wiki not working

Description
JavaScript with Wiki not working on the exportation. The mappings provided on our documentation don´t work.

${wiki:%{var t ='*'+'${Description}'.split(' ')[0] +'*'+' ${Description}'.substr('${Description}'.indexOf(' ') + 1);t.toString();}}
${wiki:%{var t ='_'+'${Description}'.split(' ')[0] +'_'+' ${Description}'.substr('${Description}'.indexOf(' ') + 1);t.toString();}}
${wiki:%{var t ='{color:red}'+'${Description}'.split(' ')[0] +'{color}'+' ${Description}'.substr('${Description}'.indexOf(' ') + 1);t.toString();}}

How to reproduce

1. Create a template with the above Javascript with Wiki
2. Create a new issue and add some text to the Description field
3. Export the template

Actual result/Attachments
It doesn't format the text as the following example:

Expected result
It should format the text according to the Javascript.