Javascript Regex - Remove single spaces NOT double spaces -

i need remove singles spaces string not double spaces.

using regex i've tried this, invalid , i'm not sure how fix it:

\s+{1,1}

this want achieve:

raw string:

"okay,  let ’s   star ted,  bret t "

after regex replace (keeping double spacing):

"okay,  let’s   started,  brett"

since javascript doesn't support lookbehinds, believe ~~have to~~ can resort callback function:

str = str.replace(/\s+/g, function(m) {     return m.length === 1 ? '' : m; });

And