jquery / JavaScript replace xth occurance -

i have string :

var str = "a a";

how replace specific else ?

eg: replace 3rd :

var str = "a 00 a";

of 1st, 2nd, etc.. ?

thanks

i split str, replace whatever index, join back

var str = "a             a";  var sp=str.split('   ');  var ind=2;  sp[ind]='00';  console.log(sp.join('   '));