How can I run a GET Request in JS and store the value in a JS variable outside of the GET Request function

Question

I am currently writing some code to create a chart using data pulled from my API in JSON format, I want to parse this data into readable variable outside of the GET Request.

The GET Request only needs calling once upon loading the page, the data is then placed into a variable which I can iterate through and plot a chart using however I am having trouble simply pulling the data from the API and storing into a variable.

    var dates = "empty";

    function httpGetAsync(URL, dates) {
        var xmlHttp = new XMLHttpRequest();
        xmlHttp.onreadystatechange = function() {
            if (xmlHttp.readyState == 4 && xmlHttp.status == 200)
            var response = JSON.parse(xmlHttp.responseText);
            console.log(response);
            dates = response;
        }
        xmlHttp.open("GET", URL, true); // true for asynchronous 
        xmlHttp.send(null);
    }

    httpGetAsync(URL, dates);

Whilst this does pull the data, I cannot send the data to the variable called dates as it does not update it, how can I do this?

Answer 1

You might be missing curly braces { and } after your if statement, not writing them will only enclose the next instruction ( in your case, assigning var response ).

Also, you don't need to pass dates as an argument to your function

var dates = "empty";

function httpGetAsync(URL) {
    var xmlHttp = new XMLHttpRequest();
    xmlHttp.onreadystatechange = function() {
        if (xmlHttp.readyState == 4 && xmlHttp.status == 200) {
            var response = JSON.parse(xmlHttp.responseText);
            console.log(response);
            dates = response;
        }
    }
    xmlHttp.open("GET", URL, true); // true for asynchronous 
    xmlHttp.send(null);
}

httpGetAsync(URL);