Question

I have this following piece of code:

var stats = {
....,
checkExistance :
function(url){
    var newUrl = url.substring(0, url.lastIndexOf("/")) + "/asyncCheckChartExistance";
    var xhrObj = stats.getXhr();

    var poolInterval = setInterval("poll()", 100);

    function poll(){
        xhrObj.open("GET", newUrl, true);
        xhrObj.send(null);

        xhrObj.onreadystatechange = function(){
            if(xhrObj.readyState === 4 && xhrObj.status === 200){
                if (xhrObj.responseText.length === true){
                    console.log("Exists!");
                    clearInterval(poolInterval);
                } else {
                    console.log("Not Yet!");
                }
            }
        }
    }
},
}

I created the stats namespace. In this namespace I’m trying to create a function which polls the server every second. I should access this function this way: stats.checkExistance(myUrl).

However it seems that the setInterval function is not able to see the poll() function. I know that this is normal behavior taking in consideration that these are nested inside another function.

If I were to write this in the Global namespace there would be no problem but I’m interested to make this work in this kind of namespace. Any ideas? Thanks!

Answer 1

when you pass a string to setInterval, it runs in the global scope, by default, where poll would not be defined since it only exists in the scope of the checkExistance function.

To fix the issue, pass an anonymous function to setInterval instead:

var poolInterval = setInterval(function () {
    poll();
}, 100);

Passing an anonymous function is usually the best idea as it allows you to write any javascript expressions/statements for the interval instead of just calling one function.