I have a string like

var str= , this,  is a ,,, test string , , to find regex,,in js.  , ;

in which there are multiple spaces in beginning,middle and end of string with commas. i need this string in

var str=this is a test string to find regex in js.;

i found many regex in forum removing spaces , commas separately but i could not join them to remove both.

Please give explanation of regex syntex to if possible .

Thanks in advance