function startWith ( s1, s2 ) {
  return ( s1.slice(0,s2.length) == s2 )
}

show(startWith("prova aaa", "prova"));
show(startWith("prova aaa", "pw"));

function string2int ( s ) {
  var result = 0;
  for ( var n = 0 ; n < s.length; n++) result = 10*result + (s[n]-"0");
  return result;
}

show(string2int("34"));show(string2int("24"));

function minArray ( v ) {
  var min = v[0];
  for (i in v) if (v[i] < min ) min = v[i];
  return min;
}

print(minArray( [ 4,22,2,102,1 ]));

function containsN ( a, n ) {
  var found=false;
  
  for ( var i=0; ! found && i<a.length ; i++ )
    if ( a[i] == n ) found = true;
  
  return found;
}

show( containsN( [ 4,22,2,102,1 ] , 21 ));