JSFiddle - React, Tailwind, and code Playground

JavaScript

function f(x,y,z,r){
  for( r=0, z=RegExp(z)
     ; x<y
     ; r+=+z.test(''+x++)
     );
  return r;
}

alert( f(0,1e6,2) );

function F(x,y,z,r){
  for( r=0
     ; x<y
     ; r+=+!!~(''+x++).indexOf(z)
     );
  return r;
}


alert( F(0,1e6,2) );