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Re: Reverse elements in array, they can be integers or strings.

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Denis McMahon <denismfmcmahon@gmail.com> writes:

> On Sat, 16 May 2015 15:00:42 +0200, Evertjan. wrote:
>
>> jonas.thornvall@gmail.com wrote on 16 mei 2015 in comp.lang.javascript:
>
>>> var arrLength; 
>>> arrLength=thisArr.length;
>>> for (i=arrLength;i>=0;i--){
>>>      thisElement=thisArr[i];
>
>> this will give an ERROR,
>> as the highest indexed element has an index of i-1
>
> Will it?

The code is wrong, but whether it "gives and ERROR" depends on what
was meant by that.

> Given i starting at thisArr.length and executing an i-- before accessing 
> the array, I don't think it will give that error, the error will be on 
> the pass after i == 0, as it will then decrement i and execute the loop 
> with i having a value of -1, which is an illegal array index.

You've got the place where the decrement happens mixed up -- it is done
after each execution of the loop body, so the loop above initially
accesses an undefined element, and then accesses all of the defined
elements in sequence.  An index of -1 is not used (though i == -1 at the
end of the loop's execution).

> All of the following are valid in c-type languages where 0 is "falsey", 
> numbers other than 0 are "truthy" and arrays are 0 indexed:
>
> for (var i = arr.length; i > 0; i--) {
> // do something with arr[i]
> }
>
> for (var i = arr.length; i; i--) {
> // do something with arr[i]
> }

No, these are both wrong.  They access an undefined element first, and
neither accesses element 0.

> var i = arr.length;
> while (i--) {
> // do something with arr[i]
> }

This one is correct.

<snip>
-- 
Ben.

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Reverse elements in array, they can be integers or strings. jonas.thornvall@gmail.com - 2015-05-16 02:03 -0700
  Re: Reverse elements in array, they can be integers or strings. jonas.thornvall@gmail.com - 2015-05-16 02:10 -0700
    MAX_SAFE_INTEGER & MIN_SAFE_INTEGER, was Re: Reverse elements in array, they can be integers or strings. "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2015-05-16 12:03 +0200
  Re: Reverse elements in array, they can be integers or strings. "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2015-05-16 11:37 +0200
    Re: Reverse elements in array, they can be integers or strings. jonas.thornvall@gmail.com - 2015-05-16 02:58 -0700
      Re: Reverse elements in array, they can be integers or strings. "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2015-05-16 12:22 +0200
        Re: Reverse elements in array, they can be integers or strings. jonas.thornvall@gmail.com - 2015-05-16 03:44 -0700
          Re: Reverse elements in array, they can be integers or strings. "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2015-05-16 14:52 +0200
            Re: Reverse elements in array, they can be integers or strings. jonas.thornvall@gmail.com - 2015-05-16 06:09 -0700
              Re: Reverse elements in array, they can be integers or strings. "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2015-05-16 15:30 +0200
      Re: Reverse elements in array, they can be integers or strings. jonas.thornvall@gmail.com - 2015-05-16 03:37 -0700
        Re: Reverse elements in array, they can be integers or strings. "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2015-05-16 15:00 +0200
          Re: Reverse elements in array, they can be integers or strings. jonas.thornvall@gmail.com - 2015-05-16 06:24 -0700
            Re: Reverse elements in array, they can be integers or strings. "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2015-05-16 15:54 +0200
              Re: Reverse elements in array, they can be integers or strings. jonas.thornvall@gmail.com - 2015-05-16 07:01 -0700
                Re: Reverse elements in array, they can be integers or strings. "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2015-05-16 21:05 +0200
          Re: Reverse elements in array, they can be integers or strings. Denis McMahon <denismfmcmahon@gmail.com> - 2015-05-16 23:07 +0000
            Re: Reverse elements in array, they can be integers or strings. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-05-17 00:28 +0100
              Re: Reverse elements in array, they can be integers or strings. Denis McMahon <denismfmcmahon@gmail.com> - 2015-05-17 10:37 +0000
              Re: Reverse elements in array, they can be integers or strings. "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2015-05-17 13:34 +0200
      Re: Reverse elements in array, they can be integers or strings. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-05-16 12:01 +0100
        Re: Reverse elements in array, they can be integers or strings. jonas.thornvall@gmail.com - 2015-05-16 04:14 -0700
          Re: Reverse elements in array, they can be integers or strings. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-05-16 13:11 +0100
            Re: Reverse elements in array, they can be integers or strings. jonas.thornvall@gmail.com - 2015-05-16 06:37 -0700
              Re: Reverse elements in array, they can be integers or strings. jonas.thornvall@gmail.com - 2015-05-16 06:54 -0700
                Re: Reverse elements in array, they can be integers or strings. "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2015-05-16 15:58 +0200
                Re: Reverse elements in array, they can be integers or strings. jonas.thornvall@gmail.com - 2015-05-16 07:04 -0700
                Re: Reverse elements in array, they can be integers or strings. "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2015-05-16 21:16 +0200
                Re: Reverse elements in array, they can be integers or strings. jonas.thornvall@gmail.com - 2015-05-16 07:51 -0700
                Re: Reverse elements in array, they can be integers or strings. "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2015-05-16 21:25 +0200
              Re: Reverse elements in array, they can be integers or strings. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-05-16 21:41 +0100
                Re: Reverse elements in array, they can be integers or strings. jonas.thornvall@gmail.com - 2015-05-16 16:51 -0700
                Re: Reverse elements in array, they can be integers or strings. "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2015-05-17 11:14 +0200
                Re: Reverse elements in array, they can be integers or strings. jonas.thornvall@gmail.com - 2015-05-17 03:04 -0700
                Re: Reverse elements in array, they can be integers or strings. "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2015-05-17 12:40 +0200
                Re: Reverse elements in array, they can be integers or strings. jonas.thornvall@gmail.com - 2015-05-17 06:04 -0700
                Re: Reverse elements in array, they can be integers or strings. "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2015-05-17 21:47 +0200
                Re: Reverse elements in array, they can be integers or strings. jonas.thornvall@gmail.com - 2015-05-17 15:06 -0700
                Re: Reverse elements in array, they can be integers or strings. "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2015-05-18 00:57 +0200
                Re: Reverse elements in array, they can be integers or strings. jonas.thornvall@gmail.com - 2015-05-17 17:10 -0700
                Re: Reverse elements in array, they can be integers or strings. "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2015-05-18 13:16 +0200
                Re: Reverse elements in array, they can be integers or strings. John Harris <niam@jghnorth.org.uk.invalid> - 2015-05-18 10:28 +0100
                Re: Reverse elements in array, they can be integers or strings. Denis McMahon <denismfmcmahon@gmail.com> - 2015-05-18 16:44 +0000
                Re: Reverse elements in array, they can be integers or strings. jonas.thornvall@gmail.com - 2015-05-18 10:16 -0700
                Re: Reverse elements in array, they can be integers or strings. jonas.thornvall@gmail.com - 2015-05-18 10:13 -0700
                Re: Reverse elements in array, they can be integers or strings. John Harris <niam@jghnorth.org.uk.invalid> - 2015-05-18 19:42 +0100
                Re: Reverse elements in array, they can be integers or strings. jonas.thornvall@gmail.com - 2015-05-17 02:58 -0700
            Re: Reverse elements in array, they can be integers or strings. Denis McMahon <denismfmcmahon@gmail.com> - 2015-05-16 22:41 +0000
          Re: Reverse elements in array, they can be integers or strings. "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2015-05-16 15:11 +0200
      Re: Reverse elements in array, they can be integers or strings. John Harris <niam@jghnorth.org.uk.invalid> - 2015-05-17 11:27 +0100

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