function filter(a, cb) {
  var n = [];
  each(a, function(v) {
    if (cb(v)) {
      n.push(v);
    }
  });
  return n;
}
function filter(a, cb) {
  var n = [];
  each(a, function(v) {
    if (cb(v)) {
      n.push(v);
    }
  });
  return n;
}
function filter ( a , cb ) { var n = [ ] ; each ( a , function ( v ) { if ( cb ( v ) ) { n . push ( v ) ; } } ) ; return n ; }
Returns those elements of `a` for which `cb(a)` returns truthy
Returns those elements of a for which cb ( a ) returns truthy