Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.javascript > #33164 > unrolled thread

How to perform an EXACT match for an item without looping through?

Back to article view | Back to comp.lang.javascript

Contents

  How to perform an EXACT match for an item without looping through? justaguy <lichunshen84@gmail.com> - 2017-05-02 18:49 -0700
    Re: How to perform an EXACT match for an item without looping through? JJ <jj4public@vfemail.net> - 2017-05-03 18:36 +0700
      Re: How to perform an EXACT match for an item without looping through? justaguy <lichunshen84@gmail.com> - 2017-05-03 05:58 -0700
        Re: How to perform an EXACT match for an item without looping through? JJ <jj4public@vfemail.net> - 2017-05-04 15:03 +0700
          Re: How to perform an EXACT match for an item without looping through? "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2017-05-04 10:57 +0200
          Re: How to perform an EXACT match for an item without looping through? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-05-05 18:40 +0200
        Re: How to perform an EXACT match for an item without looping through? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-05-05 19:59 +0200
          Re: How to perform an EXACT match for an item without looping through? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-05-06 02:10 +0200
    Re: How to perform an EXACT match for an item without looping through? John G Harris <niam@jghnorth.org.uk.invalid> - 2017-05-03 14:45 +0100
      Re: How to perform an EXACT match for an item without looping through? justaguy <lichunshen84@gmail.com> - 2017-05-03 07:12 -0700
      Re: How to perform an EXACT match for an item without looping through? justaguy <lichunshen84@gmail.com> - 2017-05-17 09:58 -0700
        Re: How to perform an EXACT match for an item without looping through? "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2017-05-17 19:34 +0200
          Re: How to perform an EXACT match for an item without looping through? justaguy <lichunshen84@gmail.com> - 2017-05-17 11:12 -0700
            Re: How to perform an EXACT match for an item without looping through? "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2017-05-17 20:33 +0200
              Re: How to perform an EXACT match for an item without looping through? justaguy <lichunshen84@gmail.com> - 2017-05-17 15:16 -0700
                Re: How to perform an EXACT match for an item without looping through? "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2017-05-18 11:15 +0200
                  Re: How to perform an EXACT match for an item without looping through? justaguy <lichunshen84@gmail.com> - 2017-05-19 07:58 -0700

#33164 — How to perform an EXACT match for an item without looping through?

The following won't work.  Is it doable without looping through the list?

Thanks.

<script>
	/* find EXACT match of an item from a list without looping
	in this case, the 2nd item */

	var list = "2332,123456,9922";
	
	var f = list.match(/12345/g);
	
	if (f.length == 0) {
		console.log('not found');
	}
	else {
	console.log('found');
	}
	
	
	var list = "2332,123456,9922";
	
	var f = list.indexOf('12345');
	
	console.log(f);
	
</script>

[toc] | [next] | [standalone]

#33177

On Tue, 2 May 2017 18:49:20 -0700 (PDT), justaguy wrote:
> The following won't work.  Is it doable without looping through the list?
> 
> Thanks.
> 
> <script>
> 	/* find EXACT match of an item from a list without looping
> 	in this case, the 2nd item */
> 
> 	var list = "2332,123456,9922";
> 	
> 	var f = list.match(/12345/g);
> 	
> 	if (f.length == 0) {
> 		console.log('not found');
> 	}
> 	else {
> 	console.log('found');
> 	}
> 	
> 	
> 	var list = "2332,123456,9922";
> 	
> 	var f = list.indexOf('12345');
> 	
> 	console.log(f);
> 	
> </script>

The code does work. And it doesn't even use any loop already.

[toc] | [prev] | [next] | [standalone]

#33179

On Wednesday, May 3, 2017 at 7:36:22 AM UTC-4, JJ wrote:
> On Tue, 2 May 2017 18:49:20 -0700 (PDT), justaguy wrote:
> > The following won't work.  Is it doable without looping through the list?
> > 
> > Thanks.
> > 
> > <script>
> > 	/* find EXACT match of an item from a list without looping
> > 	in this case, the 2nd item */
> > 
> > 	var list = "2332,123456,9922";
> > 	
> > 	var f = list.match(/12345/g);
> > 	
> > 	if (f.length == 0) {
> > 		console.log('not found');
> > 	}
> > 	else {
> > 	console.log('found');
> > 	}
> > 	
> > 	
> > 	var list = "2332,123456,9922";
> > 	
> > 	var f = list.indexOf('12345');
> > 	
> > 	console.log(f);
> > 	
> > </script>
> 
> The code does work. And it doesn't even use any loop already.

Sorry, it must be a misunderstanding.  For instance, list.indexOf('12345') produces "found", which is wrong because it's not the same as '123456', the latter is an item from the list while the '12345' is not.

[toc] | [prev] | [next] | [standalone]

#33188

On Wed, 3 May 2017 05:58:25 -0700 (PDT), justaguy wrote:
> 
> Sorry, it must be a misunderstanding.  For instance, list.indexOf('12345')
> produces "found", which is wrong because it's not the same as '123456',
> the latter is an item from the list while the '12345' is not.

In that case...

  var list = "2332,123456,9922";

  var f = list.split(",").indexOf("12345");
  console.log(f); //-1
  var f = list.split(",").indexOf("123456");
  console.log(f); //1

As for regexp...

  var f = list.match(/\b12345'b/g);
  if (f.length == 0) {
    console.log('not found');
  }
  else {
    console.log('found');
  }

[toc] | [prev] | [next] | [standalone]

#33189

JJ <jj4public@vfemail.net> wrote on 04 May 2017 in comp.lang.javascript:

> In that case...
> 
>   var list = "2332,123456,9922";
 
> As for regexp...
> 
>   var f = list.match(/\b12345'b/g);

That is what regex.test() is for.

>   if (f.length == 0) {
>     console.log('not found');
>   }
>   else {
>     console.log('found');
>   }

'use strict';

let list = '2332,123456,9922';

console.log(
    	( /,12345,/.test(','+list+',') )
    	    	? 'found' : 'not found'
	); // not found

console.log(
    	( /,123456,/.test(','+list+',') )
    	    	? 'found' : 'not found'
	); // found
-- 
Evertjan.
The Netherlands.
(Please change the x'es to dots in my emailaddress)

[toc] | [prev] | [next] | [standalone]

#33222

JJ wrote:

> On Wed, 3 May 2017 05:58:25 -0700 (PDT), justaguy wrote:
>> Sorry, it must be a misunderstanding.  For instance,
>> list.indexOf('12345') produces "found", which is wrong because it's not
>> the same as '123456', the latter is an item from the list while the
>> '12345' is not.
> 
> In that case...
> 
>   var list = "2332,123456,9922";
> 
>   var f = list.split(",").indexOf("12345");
>   console.log(f); //-1
>   var f = list.split(",").indexOf("123456");
>   console.log(f); //1

That would have been my suggestion, too.  (With the exception of the 
identifier, see below.)

> As for regexp...
> 
>   var f = list.match(/\b12345'b/g);
                               ^
  var f = list.match(/\b12345\b/g);

>   if (f.length == 0) {

String.prototype.match() returns “null” if there is no match, therefore
this code will throw the exception “null has no properties” in that case.  
The proper test is

  if (f === null)

Or simpler:

  if (f == null)

Or even simpler:

  if (!f)

>     console.log('not found');
>   }
>   else {
>     console.log('found');
>   }

And since double negation should be avoided in favor of clarity,

  if (f)
  {
    console.log("found");
  }
  else
  {
    console.log("not found");
  }

“f” is not a wise identifier for potential matches.

If the matches are not used, String.prototype.match() is the wrong method to 
call, and the “g”(lobal) flag is superfluous.  Instead, call 
RegExp.prototype.test():

  if (/\b12345\b/.test(list))
  {
    console.log("found");
  }
  else
  {
    console.log("not found");
  }

Note that if "the needle" is not fixed, RegExp-special characters might need 
to be escaped before passing them to the RegExp(-like) constructor.

-- 
PointedEars
FAQ: <http://PointedEars.de/faq> | <http://PointedEars.de/es-matrix>
<https://github.com/PointedEars> | <http://PointedEars.de/wsvn/>
Twitter: @PointedEars2 | Please do not cc me./Bitte keine Kopien per E-Mail.

[toc] | [prev] | [next] | [standalone]

#33224

Stefan Ram wrote:

> justaguy <lichunshen84@gmail.com> writes:
>>Sorry, it must be a misunderstanding.  For instance,
>>list.indexOf('12345') produces "found", which is wrong
>>because it's not the same as '123456', the latter is an item
>>from the list while the '12345' is not.
> 
>   So, maybe, you're looking for
> 
> f=(x,y)=>new RegExp(",([^,]*"+y+"[^,]*),").exec(","+x+",")[1];
> f("abcdefghi,jklmnopqrst,uvwxyz","mno")=="jklmnopqrst";
> 
>   then?

Good grief.

-- 
PointedEars
FAQ: <http://PointedEars.de/faq> | <http://PointedEars.de/es-matrix>
<https://github.com/PointedEars> | <http://PointedEars.de/wsvn/>
Twitter: @PointedEars2 | Please do not cc me./Bitte keine Kopien per E-Mail.

[toc] | [prev] | [next] | [standalone]

#33229

Thomas 'PointedEars' Lahn wrote:

> Stefan Ram wrote:
>> justaguy <lichunshen84@gmail.com> writes:
>>>Sorry, it must be a misunderstanding.  For instance,
>>>list.indexOf('12345') produces "found", which is wrong
>>>because it's not the same as '123456', the latter is an item
>>>from the list while the '12345' is not.
>> 
>>   So, maybe, you're looking for
>> 
>> f=(x,y)=>new RegExp(",([^,]*"+y+"[^,]*),").exec(","+x+",")[1];
   ^ ^^^^^^^            ^ ^^^^^  ^            ^^^^^^^^^^^^^^^
 [1] [2]               [3] [6]  [4]           [5][6]

>> f("abcdefghi,jklmnopqrst,uvwxyz","mno")=="jklmnopqrst";
>> 
>>   then?
> 
> Good grief.

To elaborate, this is (from left to right)

  · error-prone[^1]
  · unnecessarily incompatible[^2]
  · unnecessarily unreadable (hard to maintain)[^2][^4]
  · insufficient[^3]
  · unsafe[^4]
  · unnecessarily complicated[^5]
  · unnecessarily inefficient[^6]

IOW: Just. DO. NOT. Do. This.  Ever.

-- 
PointedEars
FAQ: <http://PointedEars.de/faq> | <http://PointedEars.de/es-matrix>
<https://github.com/PointedEars> | <http://PointedEars.de/wsvn/>
Twitter: @PointedEars2 | Please do not cc me./Bitte keine Kopien per E-Mail.

[toc] | [prev] | [next] | [standalone]

#33181

On Tue, 2 May 2017 18:49:20 -0700 (PDT), justaguy
<lichunshen84@gmail.com> wrote:

>
>
>The following won't work.  Is it doable without looping through the list?
>
>Thanks.
>
><script>
>	/* find EXACT match of an item from a list without looping
>	in this case, the 2nd item */
>
>	var list = "2332,123456,9922";
>	
>	var f = list.match(/12345/g);
>	
>	if (f.length == 0) {
>		console.log('not found');
>	}
>	else {
>	console.log('found');
>	}
>	
>	
>	var list = "2332,123456,9922";
>	
>	var f = list.indexOf('12345');
>	
>	console.log(f);
>	
></script>

Are you able to change the coding, e.g to 
  "|2332|123456|9922|" ?
Then looking for "|12345|" won't pick up "|123456|".

  John

[toc] | [prev] | [next] | [standalone]

#33182

On Wednesday, May 3, 2017 at 9:46:01 AM UTC-4, John G Harris wrote:
> On Tue, 2 May 2017 18:49:20 -0700 (PDT), justaguy
> <> wrote:
> 
> >
> >
> >The following won't work.  Is it doable without looping through the list?
> >
> >Thanks.
> >
> ><script>
> >	/* find EXACT match of an item from a list without looping
> >	in this case, the 2nd item */
> >
> >	var list = "2332,123456,9922";
> >	
> >	var f = list.match(/12345/g);
> >	
> >	if (f.length == 0) {
> >		console.log('not found');
> >	}
> >	else {
> >	console.log('found');
> >	}
> >	
> >	
> >	var list = "2332,123456,9922";
> >	
> >	var f = list.indexOf('12345');
> >	
> >	console.log(f);
> >	
> ></script>
> 
> Are you able to change the coding, e.g to 
>   "|2332|123456|9922|" ?
> Then looking for "|12345|" won't pick up "|123456|".
> 
>   John

Nice. That works, John.  Thanks.

[toc] | [prev] | [next] | [standalone]

#33335

On Wednesday, May 3, 2017 at 9:46:01 AM UTC-4, John G Harris wrote:
> On Tue, 2 May 2017 18:49:20 -0700 (PDT), justaguy
> wrote:
> 
> >
> >
> >The following won't work.  Is it doable without looping through the list?
> >
> >Thanks.
> >
> ><script>
> >	/* find EXACT match of an item from a list without looping
> >	in this case, the 2nd item */
> >
> >	var list = "2332,123456,9922";
> >	
> >	var f = list.match(/12345/g);
> >	
> >	if (f.length == 0) {
> >		console.log('not found');
> >	}
> >	else {
> >	console.log('found');
> >	}
> >	
> >	
> >	var list = "2332,123456,9922";
> >	
> >	var f = list.indexOf('12345');
> >	
> >	console.log(f);
> >	
> ></script>
> 
> Are you able to change the coding, e.g to 
>   "|2332|123456|9922|" ?
> Then looking for "|12345|" won't pick up "|123456|".
> 
>   John

Hmm.  There's a bug, that is, if a list item value is not strictly numeric data or if alphnumeric then they are also case sensitive otherwise such match technique fails.  For instance, if we replace "12345" with "123AB45", then it won't match "123ab45", I'd like it to be case insensitive.  Can we still use indexOf ?  If so, how?

Thanks.

 

[toc] | [prev] | [next] | [standalone]

#33336

justaguy <lichunshen84@gmail.com> wrote on 17 May 2017 in
comp.lang.javascript: 

> On Wednesday, May 3, 2017 at 9:46:01 AM UTC-4, John G Harris wrote:
>> On Tue, 2 May 2017 18:49:20 -0700 (PDT), justaguy
>> wrote:
>> 
>> >
>> >
>> >The following won't work.  Is it doable without looping through the
>> >list 
> ?
>> >
>> >Thanks.
>> >
>> ><script>
>> >     /* find EXACT match of an item from a list without looping
>> >     in this case, the 2nd item */
>> >
>> >     var list = "2332,123456,9922";
>> >     
>> >     var f = list.match(/12345/g);
>> >     
>> >     if (f.length == 0) {
>> >          console.log('not found');
>> >     }
>> >     else {
>> >     console.log('found');
>> >     }
>> >     
>> >     
>> >     var list = "2332,123456,9922";
>> >     
>> >     var f = list.indexOf('12345');
>> >     
>> >     console.log(f);
>> >     
>> ></script>
>> 
>> Are you able to change the coding, e.g to 
>>   "|2332|123456|9922|" ?
>> Then looking for "|12345|" won't pick up "|123456|".
>> 
>>   John
> 
> Hmm.  There's a bug, that is, if a list item value is not strictly
> numeric data or if alphnumeric then they are also case sensitive
> otherwise such match technique fails.  For instance, if we replace
> "12345" with "123AB45", then it won't match "123ab45", I'd like it to be
> case insensitive.  Can we still use indexOf ?  If so, how? 

Did not follow the thread, 
but in general change the regex

var f = list.match(/123ab45/g);

to 

var f = list.match(/123ab45/ig);



-- 
Evertjan.
The Netherlands.
(Please change the x'es to dots in my emailaddress)

[toc] | [prev] | [next] | [standalone]

#33337

On Wednesday, May 17, 2017 at 1:35:06 PM UTC-4, Evertjan. wrote:
> justaguy  wrote on 17 May 2017 in
> comp.lang.javascript: 
> 
> > On Wednesday, May 3, 2017 at 9:46:01 AM UTC-4, John G Harris wrote:
> >> On Tue, 2 May 2017 18:49:20 -0700 (PDT), justaguy
> >> wrote:
> >> 
> >> >
> >> >
> >> >The following won't work.  Is it doable without looping through the
> >> >list 
> > ?
> >> >
> >> >Thanks.
> >> >
> >> ><script>
> >> >     /* find EXACT match of an item from a list without looping
> >> >     in this case, the 2nd item */
> >> >
> >> >     var list = "2332,123456,9922";
> >> >     
> >> >     var f = list.match(/12345/g);
> >> >     
> >> >     if (f.length == 0) {
> >> >          console.log('not found');
> >> >     }
> >> >     else {
> >> >     console.log('found');
> >> >     }
> >> >     
> >> >     
> >> >     var list = "2332,123456,9922";
> >> >     
> >> >     var f = list.indexOf('12345');
> >> >     
> >> >     console.log(f);
> >> >     
> >> ></script>
> >> 
> >> Are you able to change the coding, e.g to 
> >>   "|2332|123456|9922|" ?
> >> Then looking for "|12345|" won't pick up "|123456|".
> >> 
> >>   John
> > 
> > Hmm.  There's a bug, that is, if a list item value is not strictly
> > numeric data or if alphnumeric then they are also case sensitive
> > otherwise such match technique fails.  For instance, if we replace
> > "12345" with "123AB45", then it won't match "123ab45", I'd like it to be
> > case insensitive.  Can we still use indexOf ?  If so, how? 
> 
> Did not follow the thread, 
> but in general change the regex
> 
> var f = list.match(/123ab45/g);
> 
> to 
> 
> var f = list.match(/123ab45/ig);
> 

Ok, I've made such change except I used 
var e = document.getElementById('myID').value;
then set f = list.match(/e/ig);
And when e (element value is "123ab45"), returned f is still null, how come?

Thanks.

[toc] | [prev] | [next] | [standalone]

#33338

justaguy <lichunshen84@gmail.com> wrote on 17 May 2017 in
comp.lang.javascript: 

>> Did not follow the thread, 
>> but in general change the regex
>> 
>> var f = list.match(/123ab45/g);
>> 
>> to 
>> 
>> var f = list.match(/123ab45/ig);
>> 
> 
> Ok, I've made such change except I used 
> var e = document.getElementById('myID').value;
> then set f = list.match(/e/ig);
> And when e (element value is "123ab45"), returned f is still null, how
> come? 
> 

You cannot use a js-variable e in a regex string,
at least not this way:

var e = document.getElementById('myID').value;
var f = list.match(/e/ig);

better try:

var e = document.getElementById('myID').value;
var re = new RegExp( e,'ig' );
var f = list.match(re);

Regex is very powerfull, but it is not guesswork, read the specs.

-- 
Evertjan.
The Netherlands.
(Please change the x'es to dots in my emailaddress)

[toc] | [prev] | [next] | [standalone]

#33340

On Wednesday, May 17, 2017 at 2:33:13 PM UTC-4, Evertjan. wrote:
> justaguy  wrote on 17 May 2017 in
> comp.lang.javascript: 
> 
> >> Did not follow the thread, 
> >> but in general change the regex
> >> 
> >> var f = list.match(/123ab45/g);
> >> 
> >> to 
> >> 
> >> var f = list.match(/123ab45/ig);
> >> 
> > 
> > Ok, I've made such change except I used 
> > var e = document.getElementById('myID').value;
> > then set f = list.match(/e/ig);
> > And when e (element value is "123ab45"), returned f is still null, how
> > come? 
> > 
> 
> You cannot use a js-variable e in a regex string,
> at least not this way:
> 
> var e = document.getElementById('myID').value;
> var f = list.match(/e/ig);
> 
> better try:
> 
> var e = document.getElementById('myID').value;
> var re = new RegExp( e,'ig' );
> var f = list.match(re);
> 

It still fails.  I've decided to loop through the values since it's a small loop anyway.  Thanks tho.

> Regex is very powerfull, but it is not guesswork, read the specs.
> 

[toc] | [prev] | [next] | [standalone]

#33341

justaguy <lichunshen84@gmail.com> wrote on 18 May 2017 in
comp.lang.javascript: 

>> var e = document.getElementById('myID').value;
>> var re = new RegExp( e,'ig' );
>> var f = list.match(re);
>> 
> 
> It still fails.  I've decided to loop through the values since it's a
> small loop anyway.  Thanks tho. 

Using regex containing user-input will get you into trouble anyway,
since the user does not know about its special characters.

However a loop is NOT NEEDED, try String.search():

==============
'use strict';
let e, list = '2332,123AB45,9922';

e = '123ab45'  // = document.getElementById('myID').value;
found(e, list); // true

e = '123ab4'  // = document.getElementById('myID').value;
found(e, list); // false


function found(e, list) {
	list = ',' + list.toLowerCase() + ',';
	e = ',' + e.toLowerCase() + ',';
	let f = list.search(e) != -1;
	document.write(f);
};
==============

-- 
Evertjan.
The Netherlands.
(Please change the x'es to dots in my emailaddress)

[toc] | [prev] | [next] | [standalone]

#33354

On Thursday, May 18, 2017 at 5:16:04 AM UTC-4, Evertjan. wrote:
> justaguy  wrote on 18 May 2017 in
> comp.lang.javascript: 
> 
> >> var e = document.getElementById('myID').value;
> >> var re = new RegExp( e,'ig' );
> >> var f = list.match(re);
> >> 
> > 
> > It still fails.  I've decided to loop through the values since it's a
> > small loop anyway.  Thanks tho. 
> 
> Using regex containing user-input will get you into trouble anyway,
> since the user does not know about its special characters.
> 
> However a loop is NOT NEEDED, try String.search():
> 
> ==============
> 'use strict';
> let e, list = '2332,123AB45,9922';
> 
> e = '123ab45'  // = document.getElementById('myID').value;
> found(e, list); // true
> 
> e = '123ab4'  // = document.getElementById('myID').value;
> found(e, list); // false
> 
> 
> function found(e, list) {
> 	list = ',' + list.toLowerCase() + ',';
> 	e = ',' + e.toLowerCase() + ',';
> 	let f = list.search(e) != -1;
> 	document.write(f);
> };

Interesting and good to know about the JS's "search" function.  In my code for the loop, I also turned element value and the other side of the comparison equation into uppercase to make match case insensitive.   Thanks. 

[toc] | [prev] | [standalone]

Back to top | Article view | comp.lang.javascript

csiph-web