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