How to check if value exists in this JavaScript array?

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?

5 thoughts on “How to check if value exists in this JavaScript array?”

  1. 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);
    
    Reply
  2. 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;
    }
    
    Reply
  3. 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
    Reply
  4. 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);
    
    Reply
  5. 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);
    
    Reply

Leave a Comment