How to refresh a page whenever my json data file changes

Question

So I\'ve got this local file named \'data.json\' containing various data. I want to refresh my page only when some data in the json file changes. Appreciate your help if you

Answer 1

Check this stackOverflow question and answer

Is it possible to retrieve the last modified date of a file using Javascript?

If it's on the same server as your calling function you can use XMLHttpRequest-

This example is not asynchronous, but you can make it so if you wish.

function fetchHeader(url, wch) {
    try {
        var req=new XMLHttpRequest();
        req.open("HEAD", url, false);
        req.send(null);
        if(req.status== 200){
            return req.getResponseHeader(wch);
        }
        else return false;
    } catch(er) {
        return er.message;
    }
} 
 alert(fetchHeader(location.href,'Last-Modified'));

Refresh a page using javascript or html

Ways to refresh Page Here are the first 20:

location = location
location = location.href
location = window.location
location = self.location
location = window.location.href
location = self.location.href
location = location['href']
location = window['location']
location = window['location'].href
location = window['location']['href']
location = window.location['href']
location = self['location']
location = self['location'].href
location = self['location']['href']
location = self.location['href']
location.assign(location)
location.replace(location)
window.location.assign(location)
window.location.replace(location)
self.location.assign(location)
and the last 10:

self['location']['replace'](self.location['href'])
location.reload()
location['reload']()
window.location.reload()
window['location'].reload()
window.location['reload']()
window['location']['reload']()
self.location.reload()
self['location'].reload()
self.location['reload']()
self['location']['reload']()

So simply Combine two and two together you get what you want

If you want to periodically check that

setInterval(function(){ 
//the function here 
and compare and update last_mod_date var if there changes else keep it like that

}, 3000);

Reference date comparison Example Mozilla

var

    nLastVisit = parseFloat(document.cookie.replace(/(?:(?:^|.*;)\s*last_modif\s*\=\s*([^;]*).*$)|^.*$/, "$1")),
    nLastModif = Date.parse(document.lastModified);

if (isNaN(nLastVisit) || nLastModif > nLastVisit) {
    document.cookie = "last_modif=" + Date.now() + "; expires=Fri, 31 Dec 9999 23:59:59 GMT; path=" + location.pathname;
    if (isFinite(nLastVisit)) {
        alert("This page has been changed!");
    }
}