数组推送第一次不起作用

Question

I have the following code to run a function every second

var counter=setInterval(timer, 1000);
var global = [];
function timer()
{
    var strJSON = '[{"id":"1","timeout":"2013-09-11 03:00:00"},{"id":"2","timeout":"2013-09-11 03:00:00"}]';
    var currentRequest = [];
    var obj = jQuery.parseJSON(strJSON);
    for (var i=0; i<obj.length; i++) {
        var id = obj[i].id;
        var timeout = obj[i].timeout;
        if(id in global)
        {
            alert(id+' in array');
        } else {
            alert(id+' not in array');
            alert(id+' added');
            global.push(id);
        }
    }
}

Im using it to keep the global variable updated but without duplicates. However, when the script runs, the second id is said to be added in the first run but it is not really added as i get the following output:

/** FIRST RUN **/

• 1 not in array
• 1 added
• 2 not in array
• 2 added

/** SECOND RUN **/

• 1 in array
• 2 not in array
• 2 added

/** THIRD RUN **/

• 1 in array
• 2 in array

What am i doing wrong here?

Answer 1

id in global is not used to check an element in an array. You need to use .indexOf instead.

> "1" in ["1","2"]
true
> "2" in ["1","2"]
false

property in object is to check whether an property exist in an object.

Array is 0-indexed, so "0" in ["1","2"] and "1" in ["1", "2"] would be true, but not "2" .

So you need to change

if(id in global)

to

if (global.indexOf(id) > -1)

Note: You need a shim for old browsers which doesn't support indexOf method of array.