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[jslint] Re: Calling With Too Much Parameters

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  • pauanyu
    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
    Message 1 of 8 , Aug 14, 2010
    • 0 Attachment
      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
      >
    • 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 2 of 8 , Aug 16, 2010
      • 0 Attachment
        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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