Close and re-open the tab. That should do the trick.

I can see that this only for actually turning the dialogs back on.  But if you are a web dev and you would like to see a way to possibly have some form of notification when these are off...in the case that you are using native alerts/confirms for validation or whatever.  Check this solution to detect and notify the user https://stackoverflow.com/a/23697435/1248536

In Chrome Browser go to setting , clear browsing history and then reload the page

I have the following:

    let mut my_number = 32.90;

How do I print the type of `my_number`?

Using `type` and `type_of` did not work. Is there another way I can print the number&#39;s type?

How do I print the type of a variable?

So I&#39;m trying to add Foreign Key constraints to my database as a project requirement and it worked the first time or two on different tables, but I have two tables on which I get an error when trying to add the Foreign Key Constraints. 
The error message that I get is:

&gt; ERROR 1215 (HY000): Cannot add foreign key constraint

This is the SQL I&#39;m using to create the tables, the two offending tables are `Patient` and `Appointment`.


    SET @OLD_UNIQUE_CHECKS=@@UNIQUE_CHECKS, UNIQUE_CHECKS=0;
    SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=1;
    SET @OLD_SQL_MODE=@@SQL_MODE, SQL_MODE=&#39;TRADITIONAL,ALLOW_INVALID_DATES&#39;;
    
    CREATE SCHEMA IF NOT EXISTS `doctorsoffice` DEFAULT CHARACTER SET utf8 ;
    USE `doctorsoffice` ;
    
    -- -----------------------------------------------------
    -- Table `doctorsoffice`.`doctor`
    -- -----------------------------------------------------
    DROP TABLE IF EXISTS `doctorsoffice`.`doctor` ;
    
    CREATE  TABLE IF NOT EXISTS `doctorsoffice`.`doctor` (
      `DoctorID` INT(11) NOT NULL AUTO_INCREMENT ,
      `FName` VARCHAR(20) NULL DEFAULT NULL ,
      `LName` VARCHAR(20) NULL DEFAULT NULL ,
      `Gender` VARCHAR(1) NULL DEFAULT NULL ,
      `Specialty` VARCHAR(40) NOT NULL DEFAULT &#39;General Practitioner&#39; ,
      UNIQUE INDEX `DoctorID` (`DoctorID` ASC) ,
      PRIMARY KEY (`DoctorID`) )
    ENGINE = InnoDB
    DEFAULT CHARACTER SET = utf8;
    
    
    -- -----------------------------------------------------
    -- Table `doctorsoffice`.`medicalhistory`
    -- -----------------------------------------------------
    DROP TABLE IF EXISTS `doctorsoffice`.`medicalhistory` ;
    
    CREATE  TABLE IF NOT EXISTS `doctorsoffice`.`medicalhistory` (
      `MedicalHistoryID` INT(11) NOT NULL AUTO_INCREMENT ,
      `Allergies` TEXT NULL DEFAULT NULL ,
      `Medications` TEXT NULL DEFAULT NULL ,
      `ExistingConditions` TEXT NULL DEFAULT NULL ,
      `Misc` TEXT NULL DEFAULT NULL ,
      UNIQUE INDEX `MedicalHistoryID` (`MedicalHistoryID` ASC) ,
      PRIMARY KEY (`MedicalHistoryID`) )
    ENGINE = InnoDB
    DEFAULT CHARACTER SET = utf8;
    
    
    -- -----------------------------------------------------
    -- Table `doctorsoffice`.`Patient`
    -- -----------------------------------------------------
    DROP TABLE IF EXISTS `doctorsoffice`.`Patient` ;
    
    CREATE  TABLE IF NOT EXISTS `doctorsoffice`.`Patient` (
      `PatientID` INT unsigned NOT NULL AUTO_INCREMENT ,
      `FName` VARCHAR(30) NULL ,
      `LName` VARCHAR(45) NULL ,
      `Gender` CHAR NULL ,
      `DOB` DATE NULL ,
      `SSN` DOUBLE NULL ,
      `MedicalHistory` smallint(5) unsigned NOT NULL,
      `PrimaryPhysician` smallint(5) unsigned NOT NULL,
      PRIMARY KEY (`PatientID`) ,
      UNIQUE INDEX `PatientID_UNIQUE` (`PatientID` ASC) ,
      CONSTRAINT `FK_MedicalHistory`
        FOREIGN KEY (`MEdicalHistory` )
        REFERENCES `doctorsoffice`.`medicalhistory` (`MedicalHistoryID` )
        ON DELETE CASCADE
        ON UPDATE CASCADE,
      CONSTRAINT `FK_PrimaryPhysician`
        FOREIGN KEY (`PrimaryPhysician` )
        REFERENCES `doctorsoffice`.`doctor` (`DoctorID` )
        ON DELETE CASCADE
        ON UPDATE CASCADE)
    ENGINE = InnoDB;
    
    
    -- -----------------------------------------------------
    -- Table `doctorsoffice`.`Appointment`
    -- -----------------------------------------------------
    DROP TABLE IF EXISTS `doctorsoffice`.`Appointment` ;
    
    CREATE  TABLE IF NOT EXISTS `doctorsoffice`.`Appointment` (
      `AppointmentID` smallint(5) unsigned NOT NULL AUTO_INCREMENT ,
      `Date` DATE NULL ,
      `Time` TIME NULL ,
      `Patient` smallint(5) unsigned NOT NULL,
      `Doctor` smallint(5) unsigned NOT NULL,
      PRIMARY KEY (`AppointmentID`) ,
      UNIQUE INDEX `AppointmentID_UNIQUE` (`AppointmentID` ASC) ,
      CONSTRAINT `FK_Patient`
        FOREIGN KEY (`Patient` )
        REFERENCES `doctorsoffice`.`Patient` (`PatientID` )
        ON DELETE CASCADE
        ON UPDATE CASCADE,
      CONSTRAINT `FK_Doctor`
        FOREIGN KEY (`Doctor` )
        REFERENCES `doctorsoffice`.`doctor` (`DoctorID` )
        ON DELETE CASCADE
        ON UPDATE CASCADE)
    ENGINE = InnoDB;
    
    
    -- -----------------------------------------------------
    -- Table `doctorsoffice`.`InsuranceCompany`
    -- -----------------------------------------------------
    DROP TABLE IF EXISTS `doctorsoffice`.`InsuranceCompany` ;
    
    CREATE  TABLE IF NOT EXISTS `doctorsoffice`.`InsuranceCompany` (
      `InsuranceID` smallint(5) NOT NULL AUTO_INCREMENT ,
      `Name` VARCHAR(50) NULL ,
      `Phone` DOUBLE NULL ,
      PRIMARY KEY (`InsuranceID`) ,
      UNIQUE INDEX `InsuranceID_UNIQUE` (`InsuranceID` ASC) )
    ENGINE = InnoDB;
    
    
    -- -----------------------------------------------------
    -- Table `doctorsoffice`.`PatientInsurance`
    -- -----------------------------------------------------
    DROP TABLE IF EXISTS `doctorsoffice`.`PatientInsurance` ;
    
    CREATE  TABLE IF NOT EXISTS `doctorsoffice`.`PatientInsurance` (
      `PolicyHolder` smallint(5) NOT NULL ,
      `InsuranceCompany` smallint(5) NOT NULL ,
      `CoPay` INT NOT NULL DEFAULT 5 ,
      `PolicyNumber` smallint(5) NOT NULL AUTO_INCREMENT ,
      PRIMARY KEY (`PolicyNumber`) ,
      UNIQUE INDEX `PolicyNumber_UNIQUE` (`PolicyNumber` ASC) ,
      CONSTRAINT `FK_PolicyHolder`
        FOREIGN KEY (`PolicyHolder` )
        REFERENCES `doctorsoffice`.`Patient` (`PatientID` )
        ON DELETE CASCADE
        ON UPDATE CASCADE,
      CONSTRAINT `FK_InsuranceCompany`
        FOREIGN KEY (`InsuranceCompany` )
        REFERENCES `doctorsoffice`.`InsuranceCompany` (`InsuranceID` )
        ON DELETE CASCADE
        ON UPDATE CASCADE)
    ENGINE = InnoDB;
    
    USE `doctorsoffice` ;
    
    
    SET SQL_MODE=@OLD_SQL_MODE;
    SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS;
    SET UNIQUE_CHECKS=@OLD_UNIQUE_CHECKS;



MySQL Cannot Add Foreign Key Constraint

I accidently checked the &quot;disable alerts from this site&quot; box in Chrome, and now I cannot get any window.alert to work on my localhost.

I have tried resetting the settings in advanced but no luck.

Re-enabling window.alert in Chrome

<p>I accidently checked the "disable alerts from this site" box in Chrome, and now I cannot get any window.alert to work on my localhost.</p>
<p>I have tried resetting the settings in advanced but no luck.</p>


I&#39;m currently trying to write some JavaScript to get the attribute of the class that has been clicked. I know that to do this the correct way, I should use an event listener. 
My code is as follows:

    var classname = document.getElementsByClassName(&quot;classname&quot;);
    
    var myFunction = function() {
		var attribute = this.getAttribute(&quot;data-myattribute&quot;);
        alert(attribute);
	};

    classname.addEventListener(&#39;click&#39;, myFunction(), false);

I was expecting to get an alert box every time I clicked on one of the classes to tell me the attribute but unfortunately this does not work. Can anyone help please?

(**Note** - _I can quite easily do this in `jQuery` but I would **NOT** like to use it_)

JavaScript click event listener on class

I&#39;m trying to implement a file upload API, given here :
&lt;br&gt;
&lt;a href=&quot;http://www.mediafire.com/developers/core_api/1.4/upload/#upload_top&quot;&gt;Mediafire file Upload&lt;/a&gt;

I am successfully able to upload the *Post data* &amp; *Get data*, but have no clue how to send the **x-filename** attribute, which is meant to be *Header data* as given in API guide.

My Code : 

    xmlhttp=new XMLHttpRequest();
    var formData = new FormData();
    
    formData.append(&quot;Filedata&quot;, document.getElementById(&quot;myFile&quot;).files[0]);
    
    var photoId = getCookie(&quot;user&quot;);
    // formData.append(&quot;x-filename&quot;, photoId);            //tried this but doesn&#39;t work
    // xmlhttp.setRequestHeader(&quot;x-filename&quot;, photoId);   //tried this too (gives error) [edited after diodeous&#39; answer]
    
    xmlhttp.onreadystatechange=function()
    {
        alert(&quot;xhr status : &quot;+xmlhttp.readyState);
    }
    
    var url = &quot;http://www.mediafire.com/api/upload/upload.php?&quot;+&quot;session_token=&quot;+getCookie(&quot;mSession&quot;)+&quot;&amp;action_on_duplicate=keep&quot;;
    
    xmlhttp.open(&quot;POST&quot;, url);
    // xmlhttp.setRequestHeader(&quot;x-filename&quot;, photoId);   //tried this too, doesnt work. Infact nothing gets uploaded on mediafire.  [edited after apsillers&#39; answer]
    // cant get response due to same origin policy
    xmlhttp.send(formData);

How to add header data in XMLHttpRequest when using formdata?

Is there any way that I can check if an element is visible in pure JS (no jQuery) ?

So, for example, in this page: [Performance Bikes][1], if you hover over Deals (on the top menu), a window of deals appear, but at the beginning it was not shown. It is in the HTML but it is not visible.

So, given a DOM element, how can I check if it is visible or not? I tried: 

    window.getComputedStyle(my_element)[&#39;display&#39;]);

 but it doesn&#39;t seem to be working.  I wonder which attributes should I check. It comes to my mind:

    display !== &#39;none&#39;
    visibility !== &#39;hidden&#39;

Any others that I might be missing?


  [1]: http://www.performancebike.com/bikes/Product_10052_10551_1135340_-1_1830021__1830021

Check if element is visible in DOM

Can I check if Bootstrap Modal currently Shown / Hidden Programatically? 

Like   `bool a = if(&quot;#myModal&quot;).shown();` ?

I need true/false

Can I check if Bootstrap Modal Shown / Hidden?

Right now I am using this function:

    function is_retina_device() {
    	return window.devicePixelRatio &gt; 1;
    }

But its simplicity scares me. Is there a more thorough check?

What is the best way to detect retina support on a device using JavaScript?

The issue is that when I invoke `window.close()` or `self.close()` it doesn&#39;t close the window. Now there seems to be a belief that in Chrome you can&#39;t close by script any window that is not script created. That is patently false but regardless it is supposed to still do it, even if it requires to pop up an alert to confirm. These are not happening.

So does anyone have real, functional and proven method of closing a window using something like `javascript:window.close()` or `javascript:self.close()` that actually does what is expected and something that happens just fine in every browser that is NOT Chrome based? Any suggestions would be greatly appreciated and I am looking for Javascript specific solution, nothing JQuery or third party implementation. 

**Update:** While much of what has been suggested has serious limitations and usability issues, the latest suggestion (specific to TamperMonkey) using **`// @grant        window.close`** in the script header will often do the trick even on those tabs that normally can&#39;t handle the close method. While not entirely ideal and doesn&#39;t generalized to every case, it is a good solution in my case.

window.close and self.close do not close the window in Chrome

I&#39;ve logged the following [Chrome bug][1], which has led to many serious and non-obvious memory leaks in my code:

(These results use Chrome Dev Tools&#39; [memory profiler][2], which runs the GC, and then takes a heap snapshot of everything not garbaged collected.)

In the code below, the `someClass` instance is garbage collected (good):

    var someClass = function() {};

    function f() {
      var some = new someClass();
      return function() {};
    }

    window.f_ = f();

But it won&#39;t be garbage collected in this case (bad):

    var someClass = function() {};

    function f() {
      var some = new someClass();
      function unreachable() { some; }
      return function() {};
    }

    window.f_ = f();

And the corresponding screenshot:

![screenshot of Chromebug][3]

It seems that a closure (in this case, `function() {}`) keeps all objects &quot;alive&quot; if the object is referenced by any other closure in the same context, whether or not if that closure itself is even reachable.

My question is about garbage collection of closure in other browsers (IE 9+ and Firefox). I am quite familiar with webkit&#39;s tools, such as the JavaScript heap profiler, but I know little of other browsers&#39; tools, so I haven&#39;t been able to test this.

**In which of these three cases will IE9+ and Firefox garbage collect the** `someClass` **instance?**


  [1]: http://crbug.com/315190
  [2]: https://developers.google.com/chrome-developer-tools/docs/heap-profiling
  [3]: http://i.stack.imgur.com/ZSVf0.png

How JavaScript closures are garbage collected

I&#39;m working on a Chrome extension to be used as an internal tool. Its required behavior is:

 1. As a page action, enable an address bar icon when looking at certain intranet pages.
 2. when the user clicks the icon, identify all files of a certain media type (say, .jpg) on the page, and
 3. silently save them all to a directory on the user&#39;s local drive.

[This question has been asked before][1], but the answer then was &quot;[use NPAPI][2]&quot;, and [NPAPI is now derelict][3].

So, what is the currently available way to achieve this? The ones I&#39;ve looked at are:

 - The [chrome.FileSystem][4] API --- but this does not save files in any user-accessible location. Instead the stored files are [hidden behind obfuscated names][5] in an undocumented directory. User requires that the files be stored under their original names in an accessible directory.
 - [The HTML5 download attribute][6], by creating a data: URL and programmatically clicking it. This pops up a &quot;save as...&quot; dialog for each file, which is unacceptable when there are a hundred assets on a single page. User requires that the files be downloaded without further interaction beyond the single icon click.
 - The [Chrome Download API][7], but that is only available in the beta and dev channels. User requires this extension work with mainstream Chrome. 
 - Use the [Native Messaging API][8] by creating a small .exe that simply saves a file to disk, and then pass the .jpg as a blob to it. This seems very cumbersome and I am not even sure how to reliably pass large blobs to EXEs like that.

Is there another approach I can try?

  [1]: https://stackoverflow.com/questions/2153979/chrome-extension-how-to-save-a-file-on-disk
  [2]: https://stackoverflow.com/questions/2153979/chrome-extension-how-to-save-a-file-on-disk
  [3]: http://blog.chromium.org/2013/09/saying-goodbye-to-our-old-friend-npapi.html
  [4]: http://developer.chrome.com/apps/fileSystem.html
  [5]: https://stackoverflow.com/questions/11676584/where-does-persistent-file-system-storage-store-with-chrome
  [6]: http://updates.html5rocks.com/2011/08/Downloading-resources-in-HTML5-a-download
  [7]: http://developer.chrome.com/extensions/downloads.html
  [8]: http://developer.chrome.com/extensions/messaging.html#native-messaging

How can a Chrome extension save many files to a user-specified directory?

I would like to put a button in my app, if you press it it will get the contents of everything that was written to the console and email it to me (for reporting bugs). I know I can keep a variable around and every time I do a console.log also append the message to that variable but I am trying to keep the memory consumption of the app low so it would be much more efficient just to grab it from the console.

Is there a way to retrieve the console messages from javascript?

How to read from Chrome&#39;s console in JavaScript

I know this this has been asked in numerous posts but honestly I don&#39;t get them. I am new to JavaScript, Chrome Extensions and everything and I have this class assignment.
So I need to make a plugin that would count DOM objects on any given page using Cross Domain Requests. 
I&#39;ve been able to achieve this so far using Chrome Extension API&#39;s. 
Now the problem is I need to show the data on my popup.html page from the contentScript.js file. 
I don&#39;t know how to do that I&#39;ve tried reading the documentation but messaging in chrome I just can&#39;t understand what to do. 

following is the code so far. 

manifest.json

    {
	&quot;manifest_version&quot;:2,

	&quot;name&quot;:&quot;Dom Reader&quot;,
	&quot;description&quot;:&quot;Counts Dom Objects&quot;,
	&quot;version&quot;:&quot;1.0&quot;,

	&quot;page_action&quot;: {
		&quot;default_icon&quot;:&quot;icon.png&quot;,
		&quot;default_title&quot;:&quot;Dom Reader&quot;,
		&quot;default_popup&quot;:&quot;popup.html&quot;
	},

	&quot;background&quot;:{
		&quot;scripts&quot;:[&quot;eventPage.js&quot;],
		&quot;persistent&quot;:false
	},

	&quot;content_scripts&quot;:[
		{
			&quot;matches&quot;:[&quot;http://pluralsight.com/training/Courses/*&quot;, &quot;http://pluralsight.com/training/Authors/Details/*&quot;,                                          &quot;https://www.youtube.com/user/*&quot;, &quot;https://sites.google.com/site/*&quot;, &quot;http://127.0.0.1:3667/popup.html&quot;],
			&quot;js&quot;:[&quot;domReader_cs.js&quot;,&quot;jquery-1.10.2.js&quot;]
			//&quot;css&quot;:[&quot;pluralsight_cs.css&quot;]
		}
	],

	&quot;permissions&quot;:[
		&quot;tabs&quot;,
		&quot;http://pluralsight.com/*&quot;,
        &quot;http://youtube.com/*&quot;,
        &quot;https://sites.google.com/*&quot;,
        &quot;http://127.0.0.1:3667/*&quot;
	]

		


popup.html

    &lt;!doctype html&gt;
    &lt;html&gt;
    
        &lt;title&gt; Dom Reader &lt;/title&gt;    
        &lt;script src=&quot;jquery-1.10.2.js&quot; type=&quot;text/javascript&quot;&gt;&lt;/script&gt;
        &lt;script src=&quot;popup.js&quot; type=&quot;text/javascript&quot;&gt;&lt;/script&gt;
    
    &lt;body&gt;
        &lt;H1&gt; Dom Reader &lt;/H1&gt;
        &lt;input type=&quot;submit&quot; id=&quot;readDom&quot; value=&quot;Read DOM Objects&quot; /&gt;
        
       &lt;div id=&quot;domInfo&quot;&gt;
        
        &lt;/div&gt;
    &lt;/body&gt;
    &lt;/html&gt;

eventPage.js

    var value1,value2,value3;

    chrome.runtime.onMessage.addListener(function (request, sender, sendResponse) {
    if (request.action == &quot;show&quot;) {
        chrome.tabs.query({ active: true, currentWindow: true }, function (tabs) {
            chrome.pageAction.show(tabs[0].id);
        });
    }
    
    value1 = request.tElements;
    });

popup.js

    $(function (){
    $(&#39;#readDom&#39;).click(function(){
    chrome.tabs.query({active: true, currentWindow: true}, function (tabs){
        chrome.tabs.sendMessage(tabs[0].id, {action: &quot;readDom&quot;});
        
     });
    });
    });

contentScript

    var totalElements;
    var inputFields;
    var buttonElement;

    chrome.runtime.onMessage.addListener(function (request, sender, sendResponse){
    if(request.action == &quot;readDom&quot;){
        
        totalElements = $(&quot;*&quot;).length;
        inputFields = $(&quot;input&quot;).length;
        buttonElement = $(&quot;button&quot;).length;
        
       
    }
    })

    chrome.runtime.sendMessage({ 
    action: &quot;show&quot;, 
    tElements: totalElements, 
    Ifields: inputFields, 
    bElements: buttonElement 

    });

Any help would be appreciated and please avoid any noobness I did :) 




Content Type	Original Author	Original Content on Stackoverflow
Question	max	View Question on Stackoverflow
Solution 1 - Javascript	user2824854	View Answer on Stackoverflow
Solution 2 - Javascript	DeadlyChambers	View Answer on Stackoverflow
Solution 3 - Javascript	Deshani Tharaka	View Answer on Stackoverflow

Re-enabling window.alert in Chrome

Javascript Problem Overview

Javascript Solutions

Solution 1 - Javascript

Solution 2 - Javascript

Solution 3 - Javascript

MySQL Cannot Add Foreign Key Constraint

How do I print the type of a variable?

Attributions