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Re: [jslint] Re: Calling With Too Much Parameters

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  • Rob Richardson
    Yes, until one of the implementations looked like this: if (arguments.length === 1 && typeof(arguments[0]) === object ) { var arg = arguments[0]; // TODO:
    Message 1 of 8 , Aug 16 7:44 AM
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      Yes, until one of the implementations looked like this:

      if (arguments.length === 1 && typeof(arguments[0]) === 'object') {
      var arg = arguments[0]; // TODO: move var definition to the top
      if (arg.length && arg.length > 0) {
      // ASSUME: Array
      for ( var i = 0; i < arg.length; i++ ) {
      option.arrayelem[i] = arg[i];
      }
      } else {
      // ASSUME: Object
      for ( var prop in arg ) {
      if ( arg.hasOwnProperty(prop) ) {
      option[prop] = arg[prop];
      }
      }
      }
      return;
      }

      ... yeah, I'll grant you could swap this to be:

      ...
      var arg = key;
      ...

      But in this case you couldn't:

      if (arguments.length > 2) {
      // ASSUME: they passed in the array as items instead of as an array
      var arg = Array.prototype.slice.call(arguments); // TODO: move var
      definition to the top
      for ( var i = 0; i < arg.length; i++ ) {
      option.arrayelem[i] = arg[i];
      }
      }

      The dilemma is that because the contract for this function is so diverse in
      number and type of arguments passed, sometimes it's just easier to define the
      function with no input parameters and use the arguments (fake) array to parse
      out what you're trying to do instead. Because the arguments array is always
      available, I can't just look at the function definition and the caller and
      positively identify you called me in a way I didn't expect. And because
      different implementations may use more or less arguments in the function, I
      can't from a static analysis point of view know that you called me with too many
      or too few arguments or the incorrect data type(s) to match the implementation
      you were looking for. ... or rather if you figure out a good way to do it, I'll
      sign up. Thus far, I've only been able to prove this by unit test.

      Rob

      ________________________________
      From: pauanyu <pcxunlimited@...>
      To: jslint_com@yahoogroups.com
      Sent: Sat, August 14, 2010 4:15:39 AM
      Subject: [jslint] Re: Calling With Too Much Parameters


      Yeah, I get the idea. But couldn't that function be written like this, with the
      same effect?

      var f = function (key, value) {
      var option = {}; // Options stored in a stateful mechanism

      if (arguments.length === 2 && typeof key === 'string') {
      // Called as f("setting", value);
      option[key] = value;
      return;
      }

      if (arguments.length === 1 && typeof key === 'string') {
      // Called as f("setting");
      return option[key];
      }

      if (arguments.length === 0) {
      // Called as f();
      option.init();
      return;
      }

      // Other implementations here

      throw {
      message: "You called this function incorrectly",
      arguments: arguments
      };
      };

      --- In jslint_com@yahoogroups.com, Rob Richardson <erobrich@...> wrote:
      >
      > Imagine a function whose body looked like so:
      >
      > var f = function () {
      > var option = {}; // Options stored in a stateful mechanism
      >
      > if ( arguments.length === 2 && typeof(arguments[0]) === 'string' ) {
      > // Called as f("setting",value);
      > option[arguments[0]] = arguments[1];
      > return;
      > }
      >
      > if ( arguments.length === 1 && typeof(arguments[0]) === 'string' ) {
      > // Called as f("setting");
      > return option[arguments[0]];
      > }
      >
      > if ( arguments.length === 0 ) {
      > // Called as f();
      > option.init();
      > return;
      > }
      >
      > // Other implementations here
      >
      > throw {
      > message: "You called this function incorrectly",
      > arguments: arguments
      > };
      > }
      >
      > Rob
      >
      > ________________________________
      > From: pauanyu <pcxunlimited@...>
      > To: jslint_com@yahoogroups.com
      > Sent: Thu, August 12, 2010 8:36:50 PM
      > Subject: [jslint] Re: Calling With Too Much Parameters
      >
      >
      > Just one question... how is that function any different from this one?
      >
      > var f = function (a, b) {
      > // ...
      > };
      >
      > --- In jslint_com@yahoogroups.com, Rob Richardson <erobrich@> wrote:
      > >
      > > This is totally valid (albeit confusing):
      > >
      > > var f = function () {
      > > // FRAGILE: Error check arguments.length and resulting vars for presence
      >of
      >
      >
      >
      > > value before using
      > > var a = arguments[0];
      > > var b = arguments[1];
      > > ...
      > > }
      > >
      > > A function like this could correctly be called in all these cases:
      > >
      > > f(1,2,3,4,5);
      > >
      > > f(1,2,3);
      > >
      > > f({a: 1, b: 2, c: 3});
      > >
      > > f();
      > >
      > > The jQuery UI suite uses this technique a lot -- optionally pass in a
      >settings
      >
      >
      >
      > > initialization object on first run, pass in a setting name and get back the
      > > current value, pass in a setting name and a new value to set it. The main
      > > jQuery framework also uses this technique a lot.
      > >
      > > I like the idea of JSLint knowing that a function was called with a different
      >
      >
      > > number of arguments than it accepts or with arguments that don't match the
      > > definition, but because function overloading is a standard API development
      > > technique, I can see it easily becoming more distracting than helpful. If it
      >
      >
      > > could also parse my docs and validate usages match my intent ... and drive my
      >
      >
      > > car and clean my kitchen and read my mind. :D It seems a carefully built
      >set
      >
      >
      > > of unit tests that run on each commit better accounts for potential mistakes

      >in
      >
      > >
      > > this arena.
      > >
      > > Rob
      > >
      > >
      > > ________________________________
      > > From: Jean-Charles Meyrignac <jcmeyrignac@>
      > > To: jslint_com@yahoogroups.com
      > > Sent: Tue, August 10, 2010 11:57:59 PM
      > > Subject: Re: [jslint] Re: Calling With Too Much Parameters
      > >
      > >
      > > On Wed, Aug 11, 2010 at 7:49 AM, pauanyu <pcxunlimited@> wrote:
      > >
      > > >
      > > >
      > > > Don't forget that it's possible to access the non-named parameters using
      > > > the "arguments" object.
      > > >
      > > > Thanks, I forgot that.
      > >
      > > > I suppose if the function does not access the arguments object, then
      > > > throwing a warning or error in that case might be nice.
      > > >
      > > > A warning is enough, and would help locating weird calls.
      > >
      > > > In any case, if the function is called with more arguments than it
      expects,
      > > > it simply ignores the excess. I'm not sure why that would cause a bug in
      >the
      > > > plugin.
      > > >
      > > > The routine was called with arguments (url, login, password, callback).
      > > And the routine was declared with (url, server, callback), with server =
      > > {login, password}
      > > So 'password' was used instead of 'callback'.
      > > It seems that a refactoring gone wrong..
      > >
      > > JC
      >
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