Total noob here, I'm currently studying regex in javascript. I have a function that is supposed to pick numbers between 0 and 9 from a string. The function works fine as long as the variable it searches has letters or numbers, however when a null value is entered it gives out the following error:

Uncaught: TypeError: Cannot read property 'toString' of null

How can I fix this? Thank you in advance.

Here is the code:

var lause  = "s0m3 p30pl3";

function tulostanumerot();

var numerot = /[0-9]/g;

   var testi = numerot.test(0-9);



   var setti = lause.match(numerot);

   if (testi === true) {

    console.log(setti.toString());

}

   else {

   console.log("Ei numeroita!");

};