Question

How would I check in my array of objects, if a specific item exists (in my case MachineId with id 2)?

[{"MachineID":"1","SiteID":"20"},{"MachineID":"2","SiteID":"20"},{"MachineID":"3","SiteID":"20"},{"MachineID":"4","SiteID":"20"}]

I tried this:

if (index instanceof machineIds.MachineID) {
    alert('value is Array!');
} else {
    alert('Not an array');
}

Answer 1

In cross browser way you may use jQuery.grep() method for it:

var item = $.grep(machineIds, function(item) {
    return item.MachineID == index;
});

if (item.length) {
    alert("value is Array!");
}