JavaScript - Array item not being found

Question

For some reason, the result here is coming up as false, yet the array contains that particular dateId.

See code below:

var pollOptions = [
  {"dateId": "183738", "answer": false},
  {"dateId": "183738", "answer": true}
];

var theDate = "183738";
var doesDateExist = theDate in pollOptions


document.getElementById("demo").innerHTML = doesDateExist;

score 1 · Accepted Answer · answered Apr 08 '20 at 10:28

1

in operator works for objects (not on arrays). You can use .some() method to check the presence of a specific value in an array of objects:

var pollOptions = [
  {"dateId": "183738", "answer": false},
  {"dateId": "183738", "answer": true}
];

var theDate = "183738";
var doesDateExist = pollOptions.some(({ dateId }) => dateId === theDate);


document.getElementById("demo").innerHTML = doesDateExist;

<div id="demo"></div>

answered Apr 08 '20 at 10:28

Mohammad Usman

37,952
20
92
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Thanks this is perfect :) If i wanted to get the "answer" value from the key I am searching for, how woild I do this? – Darryl Apr 08 '20 at 10:39
@DarrylBartlett You mean you will have this type of code? `theAnswer = false` – Mohammad Usman Apr 08 '20 at 10:49
@Mohammed Usman - Yeah that's right. So if I was searching for 183738, it would return the answer, for example false. – Darryl Apr 08 '20 at 10:50
@DarrylBartlett If you wants to find object with multiple search filters, you can check this post... https://stackoverflow.com/questions/31831651/javascript-filter-array-multiple-conditions – Mohammad Usman Apr 08 '20 at 10:54

score 1 · Answer 2 · answered Apr 08 '20 at 10:32

1

You can use the .includes() method on an array rather an in`, which works on objects.

var pollOptions = [{"dateId": "183738", "answer": false}, {"dateId": "183738", "answer": true}];

var theDate = "183738";
var doesDateExist = pollOptions.map(item => item.dateId).includes(theDate);

document.getElementById("demo").innerHTML = doesDateExist;

Additionally, I use the .map() function to stream your object into an array only containing the dateIds. Then we can use .includes()

answered Apr 08 '20 at 10:32

Shane Creedon

1,573
1
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How could I get the "answer" out of this query as well? – Darryl Apr 08 '20 at 11:39
What do you mean? it returns true / false as you specifed – Shane Creedon Apr 08 '20 at 11:52

score 1 · Answer 3 · answered Apr 08 '20 at 10:34

var pollOptions = [{"dateId": "183738", "answer": false}, {"dateId": "183738", "answer": true}];
var theDate = "183738";

var doesDateExist  = Boolean(pollOptions.find(function(item) {
   return item.dateId === theDate
}))

console.log(doesDateExist )

JavaScript - Array item not being found

3 Answers3