GET return undefined value out function

Question

I have global variable fan_coil_ai_bi, and I use that variable to store some data which I get from request, but problem is that len_1 is 1 ( what is ok value in this case ) and len_2 is undefined (what is wrong). How that happen in my function bellow ? How to achieve that len_2 have same value like len_1 ? What is wrong with this code ?

function read_required_fields(fan_coil_id) {
    var parameters = {};

    parameters['command'] = 'read_required_fields';
    parameters['fan_coil_id'] = fan_coil_id;

    $.get("php_scripts/network_script.php", parameters, function(data) {
        fan_coil_ai_bi=data;
        alert('len_1='+fan_coil_ai_bi.length);
    }, "json");
    alert('len_2='+fan_coil_ai_bi.length);
}

Quentin · Accepted Answer · 2011-07-20 12:42:50Z

3

Asynchronous JavaScript and XML is asynchronous.

The get method means "Make an HTTP get request and when it gets a response, do this".

It does not pause execution of the function until the HTTP response arrives.

If you want to do anything with the data, do it in the callback function (or a function you call from it).

$.get("php_scripts/network_script.php", parameters, function(data) {
    fan_coil_ai_bi=data;
    alert('len_1='+fan_coil_ai_bi.length);
    alert('len_2='+fan_coil_ai_bi.length);
}, "json");

answered Jul 20, 2011 at 12:42

Quentin

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Comments

pimvdb · Accepted Answer · 2011-07-20 12:43:05Z

2

You might want to learn about asynchronous code. In your case, what's happening is:

Request is being sent
len_2 is being alerted
Request finished (there is a response), len_1 is being alerted

So when len_2 is being alerted, fan_coil_ai_bi.length has not been defined yet.

There is no possibility to solve this; rather you already have a working solution: move dependencies into the callback.

answered Jul 20, 2011 at 12:43

pimvdb

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