Test if object with attribute exists in an array using jQuery

Question

Can someone please tell me the best way to check if an object within an array of objects has a type of 11?

Below is what I have but it will alert for every object in the array, can I check the whole array and get it to alert just the once at the end?

I've seen methods like grep but I've been trying and can't get it to work. I'm using jQuery.

var x;
for (x = 0; x < objects.length; x++) {
 if (objects[x].type == 11) {
 alert("exists");
 } else {
 alert("doesnt exist");
 }
}

• Brian Cray: What's wrong with what you're using?
• Popnoodles: @BrianCray he/she is alerting every iteration
• Nope: I've seen methods like grep but I've been trying and can't get it to work. This is how you would use grep: var existGrep = jQuery.grep(objects, function(item) { return(item.type === 11); }); I only added it to show you how you get grep() to work but off course any of the other answers are more suitable/efficient like Array.some or using break as grep() will iterate through the whole array.

Answer 1

Best way is use Array.some:

var exists = objects.some(function(el) { return el.type === 11 });

In the link there is also a shim for the browser that doesn't support it.

Otherwise you can just iterate:

var exists = false;
for (var i = 0, el; !exists && (el = objects[i++]);)
 exists = el.type === 11;

Once you have the exists variable set, you can just do:

if (exists) {
 // do something
}

Outside the loop, in both cases.

Answer 2

Your code should actually do it. If you're bothered that the loop will continue uselessly, you can abort it by calling break;

if(objects[x].type == 11){
 alert("exists");
 break;
 }

Answer 3

Make it a function:

function hasObjWithType11(arr) {
 var x;
 for (x = 0; x < arr.length; x++) {
 if(arr[x].type == 11){
 return true;
 }
 }
 return false;
}
alert(hasObjWithType11([{type:1}, {type:11}]); // alerts true

Answer 4

This will do it

var exists = false;
for (var x = 0; x < objects.length; x++) {
 if(objects[x].type == 11){
 exists = true;
 break;
 }
}
if(exists){
 alert("exists");
}

• Daryl Ginn: No need for the else, it's already declared false before the loop.

Answer 5

You could make the searching code more reusable by wrapping it into a separate function. That way you can externalize the condition for easier reading:

function array_contains(a, fn)
{
 for (i = 0, len = a.length; i < len; ++i) {
 if (fn(a[i])) {
 return true;
 }
 }
 return false;
}
if (array_contains(objects, function(item) { return item.type == 11; })) {
 alert('found');
}

You could also use Array.some():

if (objects.some(function(item) {
 return item.type == 11;
})) {
 alert('exists');
}

For IE < 9, refer to the MDN documentation for a mock version.