How to check if array element exists or not in javascript?

Question

I am working with Titanium, my code looks like this:

var currentData = new Array();

if(currentData[index]!==\"\"||currentData[index]!==null||currentData[ind         


        

Answer 1

This is exactly what the in operator is for. Use it like this:

if (index in currentData) 
{ 
    Ti.API.info(index + " exists: " + currentData[index]);
}

The accepted answer is wrong, it will give a false negative if the value at index is undefined:

const currentData = ['a', undefined], index = 1;

if (index in currentData) {
  console.info('exists');
}
// ...vs...
if (typeof currentData[index] !== 'undefined') {
  console.info('exists');
} else {
  console.info('does not exist'); // incorrect!
}

Answer 2

var demoArray = ['A','B','C','D'];
var ArrayIndexValue = 2;
if(ArrayIndexValue in demoArray){
   //Array index exists
}else{
   //Array Index does not Exists
}

Answer 3

If you use underscore.js then these type of null and undefined check are hidden by the library.

So your code will look like this -

var currentData = new Array();

if (_.isEmpty(currentData)) return false;

Ti.API.info("is exists  " + currentData[index]);

return true;

It looks much more readable now.

Answer 4

This way is easiest one in my opinion.

var nameList = new Array('item1','item2','item3','item4');

// Using for loop to loop through each item to check if item exist.

for (var i = 0; i < nameList.length; i++) {
if (nameList[i] === 'item1') 
{   
   alert('Value exist');
}else{
   alert('Value doesn\'t exist');
}

And Maybe Another way to do it is.

nameList.forEach(function(ItemList)
 {
   if(ItemList.name == 'item1')
        {
          alert('Item Exist');
        }
 }

Answer 5

This also works fine, testing by type against undefined.

if (currentData[index] === undefined){return}

Test:

const fruits = ["Banana", "Orange", "Apple", "Mango"];

if (fruits["Raspberry"] === undefined){
  console.log("No Raspberry entry in fruits!")
}

Answer 6

Consider the array a:

var a ={'name1':1, 'name2':2}

If you want to check if 'name1' exists in a, simply test it with in:

if('name1' in a){
console.log('name1 exists in a')
}else
console.log('name1 is not in a')