Disable Back Button using Javascript

User tries to use back button for most of the applications and it is valid, but few of the cases is required to disable the back button and also restrict the user.

It would be very useful when the user is on payment page. Below is the code to disable the back button in Browser.

var currentURL = window.location.pathname + window.location.search;

 history.pushState(null, null, currentURL);

 window.addEventListener('popstate', function(event) {

  history.pushState(null, null, currentURL);

 });

It works in all major browsers

Trigger onchange event manually using Javascript

Below is the code to trigger onchange event for an element using javascript.

Usage of the method can be, when we want to call the onchange event on page loads or on by changing the text box value for other textbox.


if(document.fireEvent) {
    document.getElementById("myElement").fireEvent('onchange');
} else {
    var event = document.createEvent("HTMLEvents");
    event.initEvent("change",true,false);

    document.getElementById("myElement").dispatchEvent(event);
}

Whereas in jQuery, we can simply call the below method.

jQuery('myElement').change();

Javascript: trim function support in all browsers

In Javascript, when we want to remove spaces in a string, we would be using trim function which is supported in all major browsers. See below code to use trim function in Javascript.

var str = "     message to trim    ";
document.write(str.trim());  // this code will prints as message to trim in the body.

But the above trim() function doesnot support in IE. To support the same functionality in IE too, add the below code to work as expected.

if (typeof String.prototype.trim !== "function") {
    String.prototype.trim = function () {
        return this.replace(/^\s+|\s+$/g, "")
    }
}

Restrict image access from browser using HTACCESS

 When we want to restrict the image access from the browser other than the page, add the below code in htaccess file to apply.


RewriteEngine on 
RewriteCond %{HTTP_REFERER} !^http://(www\.)?localhost [NC] 
RewriteCond %{HTTP_REFERER} !^http://(www\.)?localhost.*$ [NC] 
RewriteRule \.(gif|jpg|png)$ - [F]

localhost need to be replaced by the domain name where the application is hosted. 

NOTE: Above code works in Apache (LINUX) not in windows