The window.navigator object contains information about the visitor's browser. Through this object as stated in the article title, we can access the onLine property and tell if the visitor's device is online or offline.

I created a very simple video to guide you on this topic. Watch if interested.

First Tutorial Example

<div id="res"></div>

<button id="resBtn">Detect</button>

The onLine property of the Navigator object returns a Boolean value that specifies whether the browser is in online or offline mode:

let resDiv = document.getElementById('res');
let myBtn = document.getElementById('resBtn');

myBtn.addEventListener('click',function(){
resDiv.innerHTML = "Connection:: "+navigator.onLine;
});

In this second example, we go further and see how we can utilize this javascript object and property.

You can decide to redirect users to an offline page when they lose their internet connection while navigating your site.

As you have seen in the tutorial we created a new file called offline.html where the user is redirected when he/she has no active connection.

In the example below, we check and see if there is no connection using this line code in an "if statement":: navigator.onLine == false

The window.location.href is the line where you put the page/file you want the user to be taken to. Watch tutorial

Second Tutorial Example

document.addEventListener('DOMContentLoaded',function(){

function onlineDetector(){

setTimeout(function(){
	if(navigator.onLine == false){
	window.location.href="offline.html";
	}
},1000);

}

onlineDetector();

setInterval(onlineDetector,1000);
	
});

Offline Page Code

Place this code on the offline.html page. It's on this page where you check whether the navigator.onLine == true and then take back the users to the page they were on.

document.addEventListener('DOMContentLoaded',function(){

function onlineDetector(){

setTimeout(function(){
	if(navigator.onLine == true){
	window.location.href="javascript:history.go(-1)";
	}
},1000);

}

onlineDetector();

setInterval(onlineDetector,1000);

});

The way you can truck the previous page that the user was on is to use this history object and the go()property.

Syntax

	
//Put this inside the: href="...." attribute

javascript:history.go(-1)";

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