How to check if value exists in this JavaScript array?

Question

I have a JavaScript array, where each new item added to the array gets the next incremental number. An example would be as follows (I hope Im writing this correctly):

ArrayofPeople[0] = [{"id": "529", "name": "Bob"}];
ArrayofPeople[1] = [{"id": "820", "name": "Dave"}];
ArrayofPeople[2] = [{"id": "235", "name": "John"}];

The array is named ArrayofPeople, storing multiple data points for each person.

I need to know if an element with id of 820 exists in the array or not. How would this be done?

score 11 · Accepted Answer · edited Jan 01 '16 at 16:07

11

Something like this:

function in_array(array, id) {
    for(var i=0;i<array.length;i++) {
        return (array[i][0].id === id)
    }
    return false;
}

var result = in_array(ArrayofPeople, 235);

edited Jan 01 '16 at 16:07

Peter Mortensen

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answered Oct 12 '11 at 12:47

Manuel van Rijn

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This seems to work for me if it's false, but if it's true it stops working altogether. What am I doing wrong in this check?: `if (in_array(ArrayofPeople, 235) == true) { alert("event was in array"); } else { alert("not in array"); }` – Oseer Oct 12 '11 at 13:09
because you store the id's as a string you should doe `in_array(arrayofpeople, '235')` or you need to remove the "" from the id property in the array – Manuel van Rijn Oct 12 '11 at 13:14
3

Wow, almost 4 years and nobody mentioned that this code is not working! The code will check only if the first element's id equals to the id param! change the body of the inner loop to `if(array[i][0].id === id) return true;` – A.Akram Jan 18 '16 at 10:08

gion_13 · Answer 2 · 2021-02-19T09:57:26.050

You should iterate over the array and manually check if you have a matching id:

function getPersonById(id){
    for(var i=0,l=ArrayofPeople.length;i<l;i++)
       if(ArrayofPeople[i][0].id == id)
           return ArrayofPeople[i];
    return null;
}

Of course, this is pretty inefficient. I suggest you store your objects into an associative array (a.k.a. an object) indexed by the person's id. Then, the access to a person with a certain id is immediate since objects are nothing than hash-tables:

ArrayofPeople = {};
ArrayofPeople[529] = {"id": "529", "name": "Bob"};
ArrayofPeople[820] = {"id": "820", "name": "Dave"};
ArrayofPeople[235] = {"id": "235", "name": "John"};

 function getPersonById(id){
   return id in ArrayofPeople
       ? ArrayofPeople[id]
       : null;
}

Ja͢ck · Answer 3 · 2015-06-08T23:55:21.960

You can use the relatively new Array.prototype.some() to find whether an item exists (a shim is provided in the documentation):

var ArrayofPeople = [];
ArrayofPeople[0] = [{"id": "529", "name": "Bob"}];
ArrayofPeople[1] = [{"id": "820", "name": "Dave"}];
ArrayofPeople[2] = [{"id": "235", "name": "John"}];

function in_array(array, id) 
{
    return array.some(function(item) {
        return item[0].id === id;
    });
}

console.log(in_array(ArrayofPeople, '820')); // true

score 1 · Answer 4 · edited Nov 16 '15 at 19:36

1

function IsIdInArray(array, id) {
  for (var i = 0; i < array.length; i++) {
    if (array[i].id === id)
      return true;
  }
  return false;
}

var result = IsIdInArray(ArrayofPeople, 820);

edited Nov 16 '15 at 19:36

showdev

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answered Nov 16 '15 at 19:34

Ehasanul Hoque

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Riz · Answer 5 · 2011-10-12T13:17:57.123

1

ArrayofPeople = new Array();
ArrayofPeople[0] = [{"id": "529", "name": "Bob"}];
ArrayofPeople[1] = [{"id": "820", "name": "Dave"}];
ArrayofPeople[2] = [{"id": "235", "name": "John"}];

var str = '820';
var is_found = 'not found';
for(item in ArrayofPeople){
    target = ArrayofPeople[item][0];
    if(target['id'] === str)
        is_found = 'found';
}
alert(is_found);

edited Oct 12 '11 at 13:17

answered Oct 12 '11 at 12:56

Riz

9,703
8
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54

How to check if value exists in this JavaScript array?

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