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Re: Strict violation

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  • Douglas Crockford
    ... The warning was on line 4, not on line 6.
    Message 1 of 14 , Oct 10, 2010
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      --- In jslint_com@yahoogroups.com, "pauanyu" <pcxunlimited@...> wrote:
      >
      > "use strict";
      >
      > function foo() {
      > return this.message;
      > }
      >
      > foo.call({ message: "Hello!" });
      >
      >
      > The above returns the error "Problem at line 4 character 12: Strict violation."
      >
      > Are the call and apply methods no longer allowed in ECMAScript 5 strict mode?

      The warning was on line 4, not on line 6.
    • pauanyu
      ... Indeed, which is why I said it was on line 4. My point is that JSLint is thinking that the this usage is referring to the global object, when in fact it
      Message 2 of 14 , Oct 13, 2010
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        --- In jslint_com@yahoogroups.com, "Douglas Crockford" <douglas@...> wrote:
        >
        > --- In jslint_com@yahoogroups.com, "pauanyu" <pcxunlimited@> wrote:
        > >
        > > "use strict";
        > >
        > > function foo() {
        > > return this.message;
        > > }
        > >
        > > foo.call({ message: "Hello!" });
        > >
        > >
        > > The above returns the error "Problem at line 4 character 12: Strict violation."
        > >
        > > Are the call and apply methods no longer allowed in ECMAScript 5 strict mode?
        >
        > The warning was on line 4, not on line 6.
        >

        Indeed, which is why I said it was on line 4.

        My point is that JSLint is thinking that the "this" usage is referring to the global object, when in fact it is not (because of `call`). This means that you cannot use `call` or `apply` with strict mode without JSLint spitting back an error.

        So I ask again: are call and apply banned in ECMAScript 5 strict mode, or should JSLint tolerate this?
      • Douglas Crockford
        ... No. That is why the error was not on line 6.
        Message 3 of 14 , Oct 16, 2010
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          --- In jslint_com@yahoogroups.com, "pauanyu" <pcxunlimited@...> wrote:
          >
          > --- In jslint_com@yahoogroups.com, "Douglas Crockford" <douglas@> wrote:
          > >
          > > --- In jslint_com@yahoogroups.com, "pauanyu" <pcxunlimited@> wrote:
          > > >
          > > > "use strict";
          > > >
          > > > function foo() {
          > > > return this.message;
          > > > }
          > > >
          > > > foo.call({ message: "Hello!" });
          > > >
          > > >
          > > > The above returns the error "Problem at line 4 character 12: Strict violation."
          > > >
          > > > Are the call and apply methods no longer allowed in ECMAScript 5 strict mode?
          > >
          > > The warning was on line 4, not on line 6.
          > >
          >
          > Indeed, which is why I said it was on line 4.
          >
          > My point is that JSLint is thinking that the "this" usage is referring to the global object, when in fact it is not (because of `call`). This means that you cannot use `call` or `apply` with strict mode without JSLint spitting back an error.
          >
          > So I ask again: are call and apply banned in ECMAScript 5 strict mode, or should JSLint tolerate this?


          No. That is why the error was not on line 6.
        • Stefan Weiss
          ... Excuse me, but that s not an answer to pauanyu s question. call() and apply() still exist in ES5, even in strict mode, and no static code analysis tool can
          Message 4 of 14 , Oct 16, 2010
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            On 17/10/10 02:12, Douglas Crockford wrote:
            > --- In jslint_com@yahoogroups.com, "pauanyu" <pcxunlimited@...> wrote:
            >> So I ask again: are call and apply banned in ECMAScript 5 strict
            >> mode, or should JSLint tolerate this?
            >
            > No. That is why the error was not on line 6.

            Excuse me, but that's not an answer to pauanyu's question. call() and
            apply() still exist in ES5, even in strict mode, and no static code
            analysis tool can possibly determine what -this- refers to in a function
            like

            function foo() {
            return this.message;
            }

            Throwing an unconditional error here is not a valid strategy for a
            linting tool, unless you can explain why, and how to avoid the error. I
            realize that you're very busy, but the question was valid and, IMHO,
            deserves a better explanation.


            regards,
            stefan
          • Dominic Mitchell
            ... I think the problem here is the this keyword. From the spec , Annex C: *A this
            Message 5 of 14 , Oct 17, 2010
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              On Sun, Oct 17, 2010 at 3:30 AM, Stefan Weiss <weiss@...> wrote:

              > Excuse me, but that's not an answer to pauanyu's question. call() and
              > apply() still exist in ES5, even in strict mode, and no static code
              > analysis tool can possibly determine what -this- refers to in a function
              > like
              >
              > function foo() {
              > return this.message;
              > }
              >
              > Throwing an unconditional error here is not a valid strategy for a
              > linting tool, unless you can explain why, and how to avoid the error. I
              > realize that you're very busy, but the question was valid and, IMHO,
              > deserves a better explanation.
              >

              I think the problem here is the this keyword. From the
              spec<http://www.ecma-international.org/publications/files/ECMA-ST/ECMA-262.pdf>,
              Annex C:

              *A this value of null or undefined is not converted to the global object and
              primitive values are not converted to wrapper objects.*


              Because that function isn't being used in an object context (it's not a
              constructor as it doesn't start with a capital), JSLint is warning about the
              use of this.

              -Dom


              [Non-text portions of this message have been removed]
            • pauanyu
              ... use strict ; function foo() { return this.message; } document.body.addEventListener( click , foo, true); The above returns the same error, at the same
              Message 6 of 14 , Oct 17, 2010
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                --- In jslint_com@yahoogroups.com, "Douglas Crockford" <douglas@...> wrote:
                >
                > --- In jslint_com@yahoogroups.com, "pauanyu" <pcxunlimited@> wrote:
                > >
                > > --- In jslint_com@yahoogroups.com, "Douglas Crockford" <douglas@> wrote:
                > > >
                > > > --- In jslint_com@yahoogroups.com, "pauanyu" <pcxunlimited@> wrote:
                > > > >
                > > > > "use strict";
                > > > >
                > > > > function foo() {
                > > > > return this.message;
                > > > > }
                > > > >
                > > > > foo.call({ message: "Hello!" });
                > > > >
                > > > >
                > > > > The above returns the error "Problem at line 4 character 12: Strict violation."
                > > > >
                > > > > Are the call and apply methods no longer allowed in ECMAScript 5 strict mode?
                > > >
                > > > The warning was on line 4, not on line 6.
                > > >
                > >
                > > Indeed, which is why I said it was on line 4.
                > >
                > > My point is that JSLint is thinking that the "this" usage is referring to the global object, when in fact it is not (because of `call`). This means that you cannot use `call` or `apply` with strict mode without JSLint spitting back an error.
                > >
                > > So I ask again: are call and apply banned in ECMAScript 5 strict mode, or should JSLint tolerate this?
                >
                >
                > No. That is why the error was not on line 6.
                >

                "use strict";

                function foo() {
                return this.message;
                }

                document.body.addEventListener("click", foo, true);


                The above returns the same error, at the same location. What do I need to do to convince you that this is a problem? I think JSLint should tolerate "this" when it is being used in these two ways.

                Both ways should be valid, according to ECMAScript 5 strict mode, so unless you have a reason to believe that these two use-cases should be banned...
              • Nagy Endre
                Try instead this: use strict ; var foo = function() { return this.message; }; foo.call({ message: Hello! }); or this use strict ; var foo= function() {
                Message 7 of 14 , Oct 17, 2010
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                  Try instead this:

                  "use strict";

                  var foo = function() {
                  return this.message;
                  };

                  foo.call({ message: "Hello!" });

                  or this

                  "use strict";

                  var foo= function() {
                  return this.message;
                  };

                  document.body.addEventListener("click", foo, true);



                  ________________________________
                  From: pauanyu <pcxunlimited@...>
                  To: jslint_com@yahoogroups.com
                  Sent: Sun, October 17, 2010 9:05:54 PM
                  Subject: [jslint] Re: Strict violation


                  --- In jslint_com@yahoogroups.com, "Douglas Crockford" <douglas@...> wrote:
                  >
                  > --- In jslint_com@yahoogroups.com, "pauanyu" <pcxunlimited@> wrote:
                  > >
                  > > --- In jslint_com@yahoogroups.com, "Douglas Crockford" <douglas@> wrote:
                  > > >
                  > > > --- In jslint_com@yahoogroups.com, "pauanyu" <pcxunlimited@> wrote:
                  > > > >
                  > > > > "use strict";
                  > > > >
                  > > > > function foo() {
                  > > > > return this.message;
                  > > > > }
                  > > > >
                  > > > > foo.call({ message: "Hello!" });
                  > > > >
                  > > > >
                  > > > > The above returns the error "Problem at line 4 character 12: Strict
                  >violation."
                  > > > >
                  > > > > Are the call and apply methods no longer allowed in ECMAScript 5 strict
                  >mode?
                  > > >
                  > > > The warning was on line 4, not on line 6.
                  > > >
                  > >
                  > > Indeed, which is why I said it was on line 4.
                  > >
                  > > My point is that JSLint is thinking that the "this" usage is referring to the
                  >global object, when in fact it is not (because of `call`). This means that you
                  >cannot use `call` or `apply` with strict mode without JSLint spitting back an
                  >error.
                  > >
                  > > So I ask again: are call and apply banned in ECMAScript 5 strict mode, or
                  >should JSLint tolerate this?
                  >
                  >
                  > No. That is why the error was not on line 6.
                  >

                  "use strict";

                  function foo() {
                  return this.message;
                  }

                  document.body.addEventListener("click", foo, true);

                  The above returns the same error, at the same location. What do I need to do to
                  convince you that this is a problem? I think JSLint should tolerate "this" when
                  it is being used in these two ways.

                  Both ways should be valid, according to ECMAScript 5 strict mode, so unless you
                  have a reason to believe that these two use-cases should be banned...







                  [Non-text portions of this message have been removed]
                • Douglas Crockford
                  ... There is a lot of crappy code that ES5 accepts that JSLint rejects. Your argument will not work here. The point of ES5/strict is to prohibit leaking of the
                  Message 8 of 14 , Oct 18, 2010
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                    --- In jslint_com@yahoogroups.com, "pauanyu" <pcxunlimited@...> wrote:

                    > "use strict";
                    >
                    > function foo() {
                    > return this.message;
                    > }
                    >
                    > document.body.addEventListener("click", foo, true);
                    >
                    >
                    > The above returns the same error, at the same location. What do I need to do to convince you that this is a problem? I think JSLint should tolerate "this" when it is being used in these two ways.
                    >
                    > Both ways should be valid, according to ECMAScript 5 strict mode, so unless you have a reason to believe that these two use-cases should be banned...


                    There is a lot of crappy code that ES5 accepts that JSLint rejects. Your argument will not work here.

                    The point of ES5/strict is to prohibit leaking of the global object, something that ES3 does promiscuously. ES5/strict does some of its work dynamically, and some of its work statically. JSLint does all of its work statically, so it must be even more restrictive in order to best help you get your program right. Remember that the goal of JSLint is to improve code quality, not to make you feel good about sloppy work.

                    So when JSLint sees you saying "use strict"; and then sees you use a function statement containing this, it assumes that you don't know what you are doing and it gives you a warning.

                    My advice is that you either stop using strict mode, or adopt a more professional coding style.
                  • pauanyu
                    ... In that case, could you at least change the error message to something like: Strict violation: don t use this within a function.
                    Message 9 of 14 , Oct 19, 2010
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                      --- In jslint_com@yahoogroups.com, "Douglas Crockford" <douglas@...> wrote:
                      >
                      > --- In jslint_com@yahoogroups.com, "pauanyu" <pcxunlimited@> wrote:
                      >
                      > > "use strict";
                      > >
                      > > function foo() {
                      > > return this.message;
                      > > }
                      > >
                      > > document.body.addEventListener("click", foo, true);
                      > >
                      > >
                      > > The above returns the same error, at the same location. What do I need to do to convince you that this is a problem? I think JSLint should tolerate "this" when it is being used in these two ways.
                      > >
                      > > Both ways should be valid, according to ECMAScript 5 strict mode, so unless you have a reason to believe that these two use-cases should be banned...
                      >
                      >
                      > There is a lot of crappy code that ES5 accepts that JSLint rejects. Your argument will not work here.
                      >
                      > The point of ES5/strict is to prohibit leaking of the global object, something that ES3 does promiscuously. ES5/strict does some of its work dynamically, and some of its work statically. JSLint does all of its work statically, so it must be even more restrictive in order to best help you get your program right. Remember that the goal of JSLint is to improve code quality, not to make you feel good about sloppy work.
                      >
                      > So when JSLint sees you saying "use strict"; and then sees you use a function statement containing this, it assumes that you don't know what you are doing and it gives you a warning.
                      >
                      > My advice is that you either stop using strict mode, or adopt a more professional coding style.
                      >

                      In that case, could you at least change the error message to something like:

                      Strict violation: don't use "this" within a function.
                    • Michael
                      ... A full explanation would really be helpful. This was something that was really confusing me just this morning. Especially with a lot of libraries which
                      Message 10 of 14 , Oct 19, 2010
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                        On Tue, Oct 19, 2010 at 3:17 PM, pauanyu <pcxunlimited@...> wrote:

                        >
                        >
                        > --- In jslint_com@yahoogroups.com <jslint_com%40yahoogroups.com>, "Douglas
                        > Crockford" <douglas@...> wrote:
                        > >
                        > > --- In jslint_com@yahoogroups.com <jslint_com%40yahoogroups.com>,
                        > "pauanyu" <pcxunlimited@> wrote:
                        > >
                        > > > "use strict";
                        > > >
                        > > > function foo() {
                        > > > return this.message;
                        > > > }
                        > > >
                        > > > document.body.addEventListener("click", foo, true);
                        > > >
                        > > >
                        > > > The above returns the same error, at the same location. What do I need
                        > to do to convince you that this is a problem? I think JSLint should tolerate
                        > "this" when it is being used in these two ways.
                        > > >
                        > > > Both ways should be valid, according to ECMAScript 5 strict mode, so
                        > unless you have a reason to believe that these two use-cases should be
                        > banned...
                        > >
                        > >
                        > > There is a lot of crappy code that ES5 accepts that JSLint rejects. Your
                        > argument will not work here.
                        > >
                        > > The point of ES5/strict is to prohibit leaking of the global object,
                        > something that ES3 does promiscuously. ES5/strict does some of its work
                        > dynamically, and some of its work statically. JSLint does all of its work
                        > statically, so it must be even more restrictive in order to best help you
                        > get your program right. Remember that the goal of JSLint is to improve code
                        > quality, not to make you feel good about sloppy work.
                        > >
                        > > So when JSLint sees you saying "use strict"; and then sees you use a
                        > function statement containing this, it assumes that you don't know what you
                        > are doing and it gives you a warning.
                        > >
                        > > My advice is that you either stop using strict mode, or adopt a more
                        > professional coding style.
                        > >
                        >
                        > In that case, could you at least change the error message to something
                        > like:
                        >
                        > Strict violation: don't use "this" within a function.
                        >

                        A full explanation would really be helpful. This was something that was
                        really confusing me just this morning. Especially with a lot of libraries
                        which show examples of applying a scope to a callback function. Looking at
                        it now explicit is beautiful, but as a long time JS programmer, I always
                        thought the other way was better until I did research and read into some of
                        Douglas's comments in this thread.

                        Thanks,

                        Michael


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