Prevent a webpage from navigating away using JavaScript

Question

How to prevent a webpage from navigating away using JavaScript

User · Answer

Use onunload    For jQuery  I think this works like so     window  unload function        alert  Unloading       return falseIfYouWantToButBeCareful

User · Answer

Unlike other methods presented here  this bit of code will not cause the browser to display a warning asking the user if he wants to leave  instead  it exploits the evented nature of the DOM to redirect back to the current page  and thus cancel navigation  before the browser has a chance to unload it from memory   Since it works by short-circuiting navigation directly  it cannot be used to prevent the page from being closed  however  it can be used to disable frame-busting    function          var location   window document location       var preventNavigation   function              var originalHashValue   location hash           window setTimeout function                  location hash    preventNavigation        9999   Math random                 location hash   originalHashValue             0               window addEventListener  beforeunload   preventNavigation  false       window addEventListener  unload   preventNavigation  false           Disclaimer  You should never do this  If a page has frame-busting code on it  please respect the wishes of the author

User · Answer

In Ayman s example by returning false you prevent the browser window tab from closing   window onunload   function        alert  You are trying to leave       return false

User · Answer

I ended up with this slightly different version   var dirty   false  window onbeforeunload   function         return dirty    If you leave this page you will lose your unsaved changes     null      Elsewhere I set the dirty flag to true when the form gets dirtied  or I otherwise want to prevent navigating away    This allows me to easily control whether or not the user gets the Confirm Navigation prompt   With the text in the selected answer you see redundant prompts

User · Answer

Using onunload allows you to display messages  but will not interrupt the navigation  because it is too late   However  using onbeforeunload will interrupt navigation   window onbeforeunload   function       return         Note  An empty string is returned because newer browsers provide a message such as  Any unsaved changes will be lost  that cannot be overridden   In older browsers you could specify the message to display in the prompt   window onbeforeunload   function       return  Are you sure you want to navigate away

User · Answer

The equivalent in a more modern and browser compatible way  using modern addEventListener APIs   window addEventListener  beforeunload    event    gt         Cancel the event as stated by the standard    event preventDefault         Chrome requires returnValue to be set    event returnValue             Source  https   developer mozilla org en-US docs Web Events beforeunload

User · Answer

That suggested error message may duplicate the error message the browser already displays  In chrome  the 2 similar error messages are displayed one after another in the same window   In chrome  the text displayed after the custom message is   Are you sure you want to leave this page    In firefox  it does not display our custom error message at all  but still displays the dialog    A more appropriate error message might be   window onbeforeunload   function         return  If you leave this page  you will lose any unsaved changes        Or stackoverflow style   You have started writing or editing a post

User · Answer

If you are catching a browser back forward button and don t want to navigate away  you can use   window addEventListener  popstate   function         if  window location origin      http   example com                Do something if not your domain       else if  window location href      http   example com sign-in step-1             window history go 2      Skip the already-signed-in pages if the forward button was clicked       else if  window location href      http   example com sign-in step-2             window history go -2      Skip the already-signed-in pages if the back button was clicked       else              Let it do its thing             Otherwise  you can use the beforeunload event  but the message may or may not work cross-browser  and requires returning something that forces a built-in prompt

User · Answer

The equivalent to the accepted answer in jQuery 1 11     window  on  beforeunload   function          return  Please don t leave me          JSFiddle example  altCognito s answer used the unload event  which happens too late for JavaScript to abort the navigation

[javascript] Prevent a webpage from navigating away using JavaScript

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