Javascript regex help not match char

I'm making my own markdown editor, and it does bold and italic much like stack overflow:

// **bold**
Text = Text.replace(new RegExp("\\*\\*(.+?)\\*\\*", "g"), '<strong>$1</strong>');

// *italic*
Text = Text.replace(new RegExp("\\*(.+?)\\*", "g"), '<em>$1</em>');

The problem is now that if someone want to have a series of asterix in their text like:

If you want to do A * B * C then...

This would come out as:

A B C

Stackoverflow does it well where the asterix only work if they are not touching a space character afterwards. Eg:

** Bold ** = not bold
**Bold** = bolded
* Italic * = not italic
*Italic* = italics

So I try to add in [^ ] to make it match a non space character which is a bit buggy:

// **bold**
Text = Text.replace(new RegExp("\\*\\*(.+?)\\*\\*", "g"), '<strong>$1</strong>');

// *italic*
Text = Text.replace(new RegExp("\\*[^ ](.+?)[^ ]\\*", "g"), '<em>$1</em>');

This seems to strip a character off the start and end of $1 but apart from that it works. How can I modify my regex so both bold and italic are only activated if the text contained within is not padded by any spaces?

Edit

// **bold**
Text = Text.replace(new RegExp("\\*\\*([^ ](.+?)[^ ])\\*\\*", "g"), '<strong>$1</strong>');

// *italic*
Text = Text.replace(new RegExp("\\*([^ ](.+?)[^ ])\\*", "g"), '<em>$1</em>');

But the test case:

this ** shouldnt be bold ** ewfwef

Renders as

this * shouldnt be bold * ewfwef

Put the character classes inside the capture group:

([^ ].+?[^ ])

or a bit shorter (and considers all white spaces):

(\S.+?\S)