Remove item from array in JavaScript

Question

Seen this question a lot, but cannot find something that's what i'm looking for.

onClick I push an item to an array I have, however, if there's 3 items in my array I don't want to be able to push items anymore.

var selectedData = [];

I set my empty variable.

var index = selectedData.indexOf(3);

I then get the index of my array which is 3

if (index > 3) {
  selectedData.splice(index, 1);
}

Then within my if statement I say, if my index which is 3, is bigger then 3, then splice at index and remove one.

selectedData.push(TheThing);

I then push TheThing to my array if the if statement above isn't true.

However, I have a variable var arrayLength = selectedData.length; that grabs the length, and when I console log it, it starts at 0 and splices items anything after 4. Not 3.

Any idea what i've done wrong or misunderstood? Thanks

More full example of my code

var selectedData = [];

myElement.on('click', function() {

  var index = selectedData.indexOf(3);
      if (index > 3) {
          selectedData.splice(index, 1);
      }
  var arrayLength = selectedData.length;

  console.log(arrayLength, 'the length');

});

So in short, onClick check my array and remove anything after the third that gets added into my array.

Please provide a complete example. See minimal reproducible example for guidance. — Felix Kling
– Felix Kling, Commented Nov 19, 2015 at 16:36
I don't completely get what you're trying to do with the splice, but something like if (selectedData.length < 3) selectedData.push(TheThing); will probably work better compared to messing with indexes for only pushing when you don't have 3 elements in the array. — Shilly
– Shilly, Commented Nov 19, 2015 at 16:42
Just updated question, i'll give your suggestion a try @Shilly I'm basically, adding items to an array. But if there's three items in the array I don't want to add anything. However, the index starts at 0. So it's counting my items I add into the array as 4 not 3 so the splice I put in at 3 only removes items in the array after the 4th item in — pourmesomecode
– pourmesomecode, Commented Nov 19, 2015 at 16:44

Jonah Williams · Accepted Answer · 2015-11-19 16:42:10Z

1

Do you want this to behave as a stack or a queue?

So your code here:

var index = selectedData.indexOf(3);

Is not grabbing the 3rd index - its grabbing the first index where it sees 3, or -1 if it doesn't. Replace your if statement with,

if (selectedData.length > 3) {
    selectedData.pop() // removes last element (stack)
    // or
    selectedData = selectedData.slice(1) //remove first element (queue)
}

answered Nov 19, 2015 at 16:42

Jonah Williams

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Comments

zer00ne · Accepted Answer · 2015-11-19 16:38:16Z

0

I think you need to try var arrayLength = selectedData.length -1;

You start at 0 like a normal array, but don't you start with an empty array?

Plus when you use .length, it returns the true count of the array or collection not a 0 index. `

answered Nov 19, 2015 at 16:38

zer00ne

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Comments

nahab · Accepted Answer · 2015-11-19 16:43:05Z

0

you can override push() method of your array like this:

var a = [];
a.push = function(){}

or like this

a.push = function (newEl){
  if(this.length <3){
    Array.prototype.push.call(this, newEl)
  }
}

This is not complete example because push() can take many arguments and you should to handle this case too

answered Nov 19, 2015 at 16:43

nahab

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RiccardoC · Accepted Answer · 2015-11-19 16:45:17Z

0

var index = selectedData.indexOf(3); simply give you the index of the element of the array that has value 3 Example

 selectedData = [ 0, 3 , 2];
 alert( selectedData.indexOf( 3 ) ); // this will alert "1" that is the index of the element with value "3"

answered Nov 19, 2015 at 16:45

RiccardoC

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Azad · Accepted Answer · 2015-11-19 16:48:32Z

0

you can use this scenario

var selectedData = [];

myElement.on('click', function() {

  //if selectedData length is less than 3, push items

});

answered Nov 19, 2015 at 16:48

Azad

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Comments

Grekz · Accepted Answer · 2015-11-19 20:24:09Z

0

This could work.

myElement.on('click', function() {

    if(selectedData.length > 3){
        selectedData = selectedData.splice(0, 3);
    }

    console.log(selectedData.length, 'the length');

});

answered Nov 19, 2015 at 20:24

Grekz

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