javascript find if value is NOT IN array

Question

My problem with this is that the loop keeps going into the if statement even for duplicate barcodes. I'm trying to enter the if statement only for unique barcodes but at the end of the loop myArray has duplicates in it....why?

var myArray = new Array();  var i = 0;
$("li.foo").each(function(){
   var iBarCode = $(this).attr('barcode');
   if( !( iBarCode in myArray ) ){
      myArray[i++] = iBarCode;
      //do something else
   }
});

Gazler · Accepted Answer · 2011-06-30 22:09:27Z

40

Jquery has an inArray() function.

var myArray = new Array();  var i = 0;
$("li.foo").each(function(){
   var iBarCode = $(this).attr('barcode');
   if( $.inArray(iBarCode, myArray) == -1 ){
      myArray[i++] = iBarCode;
      //do something else
   }
});

edited Jun 30, 2011 at 22:09

answered Jun 30, 2011 at 21:54

Gazler

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6 Comments

Ravan Scafi Over a year ago

your code is wrong, !($.inArray(iBarCode, myArray) fails if the element is in position 0. you should use !!~($.inArray(iBarCode, myArray) instead.

sadmicrowave Over a year ago

now my loop is not entering the if statement for any barcodes! the myArray is blank at the end

Gazler Over a year ago

sadmicrowave, I wrote the if statement incorrectly, since inArray returns -1 if not found. I have updated the answer.

sadmicrowave Over a year ago

thank you that fixed it. just curious but is there a way to check if a value is in an array without jquery? like indexOf() or something?

Gazler Over a year ago

indexOf is not supported in IE. See this question. stackoverflow.com/questions/1744310/…

|

slaphappy · Accepted Answer · 2011-06-30 21:58:08Z

9

The in keyword search for properties, for instance when you want to know if an object has some method available. Since you are looking for values, it always returns false.

You should instead use an array search function as Gazler advises.

answered Jun 30, 2011 at 21:58

slaphappy

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1 Comment

gcb Over a year ago

and if not using jquery, just use if( myArray.indexOf(iBarCode) === -1 ){ // do something else }

moose-o · Accepted Answer · 2021-04-30 13:53:00Z

0

2021 Update

let myArray = [...new Set([...document.querySelectorAll('li.foo')].map(a => a.dataset.barcode))]

Working backwards: Create an array using the spread syntax from the matching elements, which Map only the data-barcode attribute. Use that to create a new Set, then create an array from that set

answered Apr 30, 2021 at 13:53

moose-o

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