Read a text file to a variable in JavaScript

Question

I have a file that I want to read into a variable in JS to use it later

var states;
$.get('states.json', function(data) {
        states=data;
        alert(data);
        alert(states);
    }, "text");

 alert(states);

In the above code, value of states is that of the file inside the function, but it is null outside.

You need to understand how asynchronous calls work in javascript. — Matt R
– Matt R, Commented Mar 18, 2014 at 17:20
possible duplicate of How to return the response from an AJAX call? — T.J. Crowder
– T.J. Crowder, Commented Mar 18, 2014 at 17:21

T.J. Crowder · Accepted Answer · 2014-03-18 17:20:51Z

3

That's because the alert at the end runs before the file is received. Ajax is asynchronous by default.

answered Mar 18, 2014 at 17:20

community wiki

T.J. Crowder

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2 Comments

user2612159 Over a year ago

OK so my code should wait till the file is completely fetched before proceeding further.

var states; $.get('states.json', function(data) {         states=data;         alert(data);         alert(states);     }, "text");   //alert(states);   var Cstates = Ext.create('Ext.data.Store', {                //combo box data         fields: ['abbr', 'name'],         data: states     });

this is the code later in the file, can i hold it till the value is fetched into the variable??

T.J. Crowder Over a year ago

@user2612159: The point is to call whatever code you need to use the data with from within the callback, because that's when you know it's there and ready. You can't stop the execution and wait for it (or you could look at it that that's how you do that).

floatingeye · Accepted Answer · 2014-03-18 18:00:12Z

0

There's an ultra helpful function I learned recently jQuery has with AJAX that might be of use to you.

var states;
$.get('states.json', function(data) {
    states=data;
    alert(data);
    alert(states);
}, "text").done(function(result) {console.log(result);};

That should print out the states. Check out the API for AJAX here: https://api.jquery.com/jQuery.ajax/

answered Mar 18, 2014 at 18:00

floatingeye

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