You can use [typeof][1] operator. 
&lt;!-- language: lang-js --&gt;

    if( (typeof A === &quot;object&quot; || typeof A === &#39;function&#39;) &amp;&amp; (A !== null) )
    {
        alert(&quot;A is object&quot;);
    }

Note that because `typeof new Number(1) === &#39;object&#39;` while `typeof Number(1) === &#39;number&#39;;` the first syntax should be avoided.

  [1]: https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Operators/typeof

use the following 

It will return a true or false

    theObject instanceof Object

In jQuery there is [`$.isPlainObject()`][1] method for that:

&gt; Description: Check to see if an object is a plain object (created
&gt; using &quot;{}&quot; or &quot;new Object&quot;).


  [1]: http://api.jquery.com/jQuery.isPlainObject/

[The Swift Programming Language guide](https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/AutomaticReferenceCounting.html) has the following example: 

    class Person {
        let name: String
        init(name: String) { self.name = name }
        var apartment: Apartment?
        deinit { println(&quot;\(name) is being deinitialized&quot;) }
    }
     
    class Apartment {
        let number: Int
        init(number: Int) { self.number = number }
        var tenant: Person?
        deinit { println(&quot;Apartment #\(number) is being deinitialized&quot;) }
    }

    var john: Person?
    var number73: Apartment?

    john = Person(name: &quot;John Appleseed&quot;)
    number73 = Apartment(number: 73)
    
    //From Apple&#39;s “The Swift Programming Language” guide (https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/AutomaticReferenceCounting.html)

Then when assigning the apartment to the person, they use an exclamation point to &quot;unwrap the instance&quot;:

    john!.apartment = number73

What does it mean to &quot;unwrap the instance&quot;? Why is it necessary? How is it different from just doing the following:

    john.apartment = number73


I&#39;m very new to the Swift language.  Just trying to get the basics down.

&lt;br&gt;
***UPDATE:***&lt;br&gt;
The big piece of the puzzle that I was missing (not directly stated in the answers - at least not at the time of writing this) is that when you do the following:

    var john: Person?

that does NOT mean that &quot;`john` is of type `Person` and it might be nil&quot;, as I originally thought. I was simply misunderstanding that `Person` and `Person?` are completely separate types.  Once I grasped that, all of the other `?`, `!` madness, and the great answers below, made a lot more sense.

What does an exclamation mark mean in the Swift language?

The following code has a static method, `Foo()`, calling an instance method, `Bar()`:


    public sealed class Example
    {
        int count;

        public static void Foo( dynamic x )
        {
            Bar(x);
        }

        void Bar( dynamic x )
        {
            count++;
        }
    }


It compiles without error* but generates a runtime binder exception at runtime. Removing the dynamic parameter to these methods causes a compiler error, as expected.

So why does having a dynamic parameter allow the code to be compiled? ReSharper doesn&#39;t show it as an error either.

**Edit 1:** *in Visual Studio 2008

**Edit 2:** added `sealed` since it&#39;s possible that a subclass could contain a static `Bar(...)` method. Even the sealed version compiles when it&#39;s not possible that any method other than the instance method could be called at runtime.

Why does the C# compiler not fault code where a static method calls an instance method?

&gt; **Possible Duplicate:**  
&gt; [Check that value is object literal?](https://stackoverflow.com/questions/4320767/check-that-value-is-object-literal)  

&lt;!-- End of automatically inserted text --&gt;

I am working with an output that can be either null, 0, or a json object. And with that I need to come up with a means of determining if that output is indeed a real object. But I can&#39;t find anything that gives me a definitive answer as to if there is something like that in the javascript functionality or not. If there isn&#39;t is there a means otherwise that I can detect if this is an object?

javascript, is there an isObject function like isArray?

> Possible Duplicate: 
> <a href="https://stackoverflow.com/questions/4320767/check-that-value-is-object-literal" target="_blank" rel="noopener noreferrer">Check that value is object literal?</a>

I am working with an output that can be either null, 0, or a json object. And with that I need to come up with a means of determining if that output is indeed a real object. But I can't find anything that gives me a definitive answer as to if there is something like that in the javascript functionality or not. If there isn't is there a means otherwise that I can detect if this is an object?

With a Handlebars.js template like this...

    &lt;select&gt;
        &lt;option value=&quot;Completed&quot;&gt;Completed&lt;/option&gt;
        &lt;option value=&quot;OverDue&quot;&gt;OverDue&lt;/option&gt;
        &lt;option value=&quot;SentToPayer&quot;&gt;SentToPayer&lt;/option&gt;
        &lt;option value=&quot;None&quot;&gt;None&lt;/option&gt;
    &lt;/select&gt;

... and data like this...

    {
        &quot;id&quot;     : 1,
        &quot;name&quot;   : &quot;World&quot;
        &quot;status&quot; : &quot;OverDue&quot;,
        &quot;date&quot;   : &quot;2012-12-21&quot;
    }

I want to render HTML like this.

    &lt;select&gt;
        &lt;option value=&quot;Completed&quot;&gt;Completed&lt;/option&gt;
        &lt;option value=&quot;OverDue&quot; selected=&quot;selected&quot;&gt;OverDue&lt;/option&gt;
        &lt;option value=&quot;SentToPayer&quot;&gt;SentToPayer&lt;/option&gt;
        &lt;option value=&quot;None&quot;&gt;None&lt;/option&gt;
    &lt;/select&gt;

Which way is the easiest?

How to set selected select option in Handlebars template

I have read about it in other posts, but I couldn&#39;t figure it out.

I have an array,

    $scope.items = [
       {ID: &#39;000001&#39;, Title: &#39;Chicago&#39;},
       {ID: &#39;000002&#39;, Title: &#39;New York&#39;},
       {ID: &#39;000003&#39;, Title: &#39;Washington&#39;},
    ];

I want to render it as:

    &lt;select&gt;
      &lt;option value=&quot;000001&quot;&gt;Chicago&lt;/option&gt;
      &lt;option value=&quot;000002&quot;&gt;New York&lt;/option&gt;
      &lt;option value=&quot;000003&quot;&gt;Washington&lt;/option&gt;
    &lt;/select&gt;

And also I want to select the option with ID=000002.

I have read *[select][1]* and tried, but I can&#39;t figure it out.

  [1]: http://docs.angularjs.org/api/ng.directive:select



Working with select using AngularJS&#39;s ng-options

I&#39;m looking for a way to use a line break within a tooltip text element using d3.js.

    .text(&quot;test&quot; +  &quot;&lt;/br&gt;&quot; + &quot;test&quot;)


The above, and other similar efforts, don&#39;t seem to work.

There&#39;s a thread here that seems to answer it:

https://groups.google.com/forum/?fromgroups=#!topic/d3-js/GgFTf24ltjc

but the solution isn&#39;t very clear.  How would .html be used in the above situation?

.text(.html(&quot;test&quot; +  &quot;&lt;/br&gt;&quot; + &quot;test&quot;))

didn&#39;t work?

Thanks

Can you insert a line break in text when using d3.js?

When I render a highcharts-chart to a div container, how can I get access to the chart object through the div-Container?

I don&#39;t want to make the chart variable global.

    		var chart = new Highcharts.Chart({
    			chart: {
    				renderTo: &quot;testDivId&quot;,
                                    ...

I want to access the chart outside of the context above like this (pseudocode), to call functions:

    var chart = Highcharts.Chart(&quot;testDivId&quot;); //access from id
    chart.redraw();

How can I get access to a Highcharts chart through a DOM-Container?

I was told to use document.ready when I first started to use Javascript/jQuery but I never really learned why.

Might someone provide some basic guidelines on when it makes sense to wrap javascript/jquery code inside jQuery&#39;s `document.ready`? 

Some topics I&#39;m interested in:

 1. jQuery&#39;s `.on()` method: I use the `.on()` method for AJAX quite a bit (typically on dynamically created DOM elements). Should the `.on()` click handlers **always** be **inside** `document.ready`?
 2. Performance: Is it more performant to keep various javascript/jQuery objects **inside** or **outside** document.ready (also, is the performance difference significant?)?
 3. Object scope: AJAX-loaded pages can&#39;t access objects that were **inside** the prior page&#39;s document.ready, correct? They can only access objects which were **outside** document.ready (i.e., truly &quot;global&quot; objects)? 

**Update:** To follow a best practice, all my javascript (the jQuery library and my app&#39;s code) is at the **bottom** of my HTML page and I&#39;m using the `defer` attribute on the jQuery-containing scripts on my AJAX-loaded pages so that I can access the jQuery library on these pages.
 

When should I use jQuery&#39;s document.ready function?

I am using this fancy little JavaScript to highlight a field as the user hovers over it. Could you please tell me if there is a way of adding an `onclick` function which will act as a link and go to a URL?


    &lt;script&gt;
             $(function() {
                $(&#39;tr&#39;).hover(function() {
                    $(this).css(&#39;background-color&#39;, &#39;#eee&#39;);
                    $(this).contents(&#39;td&#39;).css({&#39;border&#39;: &#39;0px solid red&#39;, &#39;border-left&#39;: &#39;none&#39;, &#39;border-right&#39;: &#39;none&#39;});
                    $(this).contents(&#39;td:first&#39;).css(&#39;border-left&#39;, &#39;0px solid red&#39;);
                    $(this).contents(&#39;td:last&#39;).css(&#39;border-right&#39;, &#39;0px solid red&#39;);
                },
                function() {
                    $(this).css(&#39;background-color&#39;, &#39;#FFFFFF&#39;);
                    $(this).contents(&#39;td&#39;).css(&#39;border&#39;, &#39;none&#39;);
        			$(&#39;a#read_message.php&#39;).click(function(){ URL(); });
                });
            });
        	&lt;/script&gt;


Adding an onclick function to go to url in JavaScript?

I have a somewhat unusual issue. I&#39;ve done something like this many times:

    $(&#39;#selector&#39;).css(&#39;color&#39;,&#39;#00f&#39;);

My problem is that I create a `&lt;div id=&quot;selector&quot;&gt;`, and I call the command above and it works fine.

Now, on another event, later, I remove that element from the [DOM][1] and add it again at a later time with the same id. This element now doesn&#39;t have `color:#00f`.

Is there a way that I can add a rule in CSS, such that it will affect items that are created in the future with that same `id`/`class`? I like [jQuery][2], but anything with plain JavaScript would be fine as well.

It has to be dynamic, and I don&#39;t know the classes to put in a CSS file.  Also, I plan on changing a single attribute a few different times through the course of the application. For example, setting the `color` to `black`, to `blue`, to `red`, and back to `black`.

&lt;br/&gt;

&lt;hr/&gt;

I went with the answer from **@lucassp**, and this is what I ended up with:

    function toggleIcon(elem, classname)
    {
        if($(elem).attr(&#39;src&#39;)==&#39;img/checkbox_checked.gif&#39;)
        {
            $(elem).attr(&#39;src&#39;, &#39;img/checkbox_unchecked.gif&#39;)
            //$(&#39;.&#39;+classname).hide();//this was the old line that I removed
            $(&#39;html &gt; head&#39;).append($(&#39;&lt;style&gt;.&#39;+classname+&#39; { display:none; }&lt;/style&gt;&#39;));
        }
        else
        {
            $(elem).attr(&#39;src&#39;, &#39;img/checkbox_checked.gif&#39;)
            //$(&#39;.&#39;+classname).show();//this was the old line that I removed
            $(&#39;html &gt; head&#39;).append($(&#39;&lt;style&gt;.&#39;+classname+&#39; { display:block; }&lt;/style&gt;&#39;));
        }
    }

I also want to say that **@Nelson** is probably the most &quot;correct&quot;, though it would require more work to go into application code that always works fine, and that&#39;s not effort I want to spend at the moment.

If I had to rewrite this (or write something similar) in the future, I would look into `detach()`.

  [1]: http://en.wikipedia.org/wiki/Document_Object_Model
  [2]: http://en.wikipedia.org/wiki/JQuery


Add CSS rule via jQuery for future created elements

I understand there has been a lot of discussion on this but I have yet to find a solution to fix my needs. Basically I need to autogrow a text area not when you type but on load. I am pulling in content from a database and dependant on the user&#39;s settings an overlay is produced over the text area, but upon doing this the text areas are not scrollable therefore I need to autosize these to show all the text.

I have tried scrollHeight but this is not working great as there are multiple text boxes on the screen

Thanks

Resize text area to fit all text on load jquery

I have tried:

    const ascii = &quot;abcdefghijklmnopqrstuvwxyz&quot;
    const letter_goodness []float32  = { .0817,.0149,.0278,.0425,.1270,.0223,.0202, .0609,.0697,.0015,.0077,.0402,.0241,.0675, .0751,.0193,.0009,.0599,.0633,.0906,.0276, .0098,.0236,.0015,.0197,.0007 }
    const letter_goodness  = { .0817,.0149,.0278,.0425,.1270,.0223,.0202, .0609,.0697,.0015,.0077,.0402,.0241,.0675, .0751,.0193,.0009,.0599,.0633,.0906,.0276, .0098,.0236,.0015,.0197,.0007 }
    const letter_goodness = []float32 { .0817,.0149,.0278,.0425,.1270,.0223,.0202, .0609,.0697,.0015,.0077,.0402,.0241,.0675, .0751,.0193,.0009,.0599,.0633,.0906,.0276, .0098,.0236,.0015,.0197,.0007 }

The first declaration and initialization works fine, but the second, third and fourth don&#39;t work.

How can I declare and initialize a const array of floats?


Declare a constant array

    $array1 = array(&quot;$name1&quot; =&gt; &quot;$id1&quot;);
    
    $array2 = array(&quot;$name2&quot; =&gt; &quot;$id2&quot;, &quot;$name3&quot; =&gt; &quot;$id3&quot;);

I need a new array combining all together, i.e. it would be

    $array3 = array(&quot;$name1&quot; =&gt; &quot;$id1&quot;, &quot;$name2&quot; =&gt; &quot;$id2&quot;, &quot;$name3&quot; =&gt; &quot;$id3&quot;);

What is the best way to do this?

Sorry, I forgot, the ids will never match each other, but technically the names could, yet would not be likely, and they all need to be listed in one array.  I looked at array_merge but wasn&#39;t sure if that was best way to do this.  Also, how would you unit test this?

PHP combine two associative arrays into one array

I am interested in knowing how to convert a pandas dataframe into a NumPy array.

dataframe:

    import numpy as np
    import pandas as pd

    index = [1, 2, 3, 4, 5, 6, 7]
    a = [np.nan, np.nan, np.nan, 0.1, 0.1, 0.1, 0.1]
    b = [0.2, np.nan, 0.2, 0.2, 0.2, np.nan, np.nan]
    c = [np.nan, 0.5, 0.5, np.nan, 0.5, 0.5, np.nan]
    df = pd.DataFrame({&#39;A&#39;: a, &#39;B&#39;: b, &#39;C&#39;: c}, index=index)
    df = df.rename_axis(&#39;ID&#39;)
  
gives

    label   A    B    C
    ID                                 
    1	NaN  0.2  NaN
    2	NaN  NaN  0.5
    3	NaN  0.2  0.5
    4	0.1  0.2  NaN
    5	0.1  0.2  0.5
    6	0.1  NaN  0.5
    7	0.1  NaN  NaN

I would like to convert this to a NumPy array, as so:

    array([[ nan,  0.2,  nan],
           [ nan,  nan,  0.5],
           [ nan,  0.2,  0.5],
           [ 0.1,  0.2,  nan],
           [ 0.1,  0.2,  0.5],
           [ 0.1,  nan,  0.5],
           [ 0.1,  nan,  nan]])

How can I do this? 

----

As a bonus, is it possible to preserve the dtypes, like this?
 
    array([[ 1, nan,  0.2,  nan],
           [ 2, nan,  nan,  0.5],
           [ 3, nan,  0.2,  0.5],
           [ 4, 0.1,  0.2,  nan],
           [ 5, 0.1,  0.2,  0.5],
           [ 6, 0.1,  nan,  0.5],
           [ 7, 0.1,  nan,  nan]],
         dtype=[(&#39;ID&#39;, &#39;&lt;i4&#39;), (&#39;A&#39;, &#39;&lt;f8&#39;), (&#39;B&#39;, &#39;&lt;f8&#39;), (&#39;B&#39;, &#39;&lt;f8&#39;)])

or similar?


Convert pandas dataframe to NumPy array

I have searched for a way to resize an array in Java, but I could not find ways of resizing the array *while keeping the current elements*.

I found for example code like `int[] newImage = new int[newWidth];`, but this deletes the elements stored before.

My code would basically do this: whenever  a new element is added, the array largens by **1**. I think this could be done with dynamic programming, but I&#39;m, not sure how to implement it.

Resize an Array while keeping current elements in Java?

How do I create an empty mutable two dimensional array in Rust?

This is what I have tried so far:

    let mut state[[u8 * 4] * 4];

This produces the error

&lt;!-- language: none --&gt;

    error: expected one of `:`, `;`, `=`, or `@`, found `[`
     --&gt; src/main.rs:2:18
      |
    2 |     let mut state[[u8 * 4] * 4];
      |                  ^ expected one of `:`, `;`, `=`, or `@` here



Creating two dimensional arrays in Rust


Is there a Language supported way make a full (deep) copy of an Object in Dart?

Secondary only; are there multiple ways of doing this, and what are the differences?


Thanks for clarification!



How can I clone an Object (deep copy) in Dart?

I want to be able to create a new instance of an object by calling a method on an already instantiated object. For example, I have the object:

`organism = Organism()`

I want to be able to call `organism.reproduce()` and have two objects of type Organism. My method at this point looks like this:

    class Organism(object):
        def reproduce():
            organism = Organism()

and I&#39;m pretty sure it doesn&#39;t work (I&#39;m not really even sure how to test it. I tried the gc method in [this post][1]). So how can I make my object create a copy of itself that&#39;s accessible just like the first object I created (with `organism = Organism()`)?


  [1]: https://stackoverflow.com/questions/328851/printing-all-instances-of-a-class

Create new class instance from class method

I constructed a class with one `String` field. Then I created two objects and I have to compare them using `==` operator and `.equals()` too. Here&#39;s what I&#39;ve done:

    public class MyClass {
    	
    	String a;
    	
    	public MyClass(String ab) {
    		a = ab;
    	}
    	
    	public boolean equals(Object object2) {
    		if(a == object2) { 
    			return true;
    		}
    		else return false;
    	}
    	
    	public boolean equals2(Object object2) {
    		if(a.equals(object2)) {
    			return true;
    		}
    		else return false;
    	}
    	
    	
    	
    	public static void main(String[] args) {
    		
    		MyClass object1 = new MyClass(&quot;test&quot;);
    		MyClass object2 = new MyClass(&quot;test&quot;);
    		
    		object1.equals(object2);
    		System.out.println(object1.equals(object2));
    		
    		object1.equals2(object2);
    		System.out.println(object1.equals2(object2));
    	}
    	
    
    }

After compile it shows two times false as a result. Why is it false if the two objects have the same fields - &quot;test&quot;?

Compare two objects with .equals() and == operator

I was looking for a easy way to know bytes size of arrays and dictionaries object, like 

    [ [1,2,3], [4,5,6] ] or { 1:{2:2} }

Many topics say to use pylab, for example:

    from pylab import *
    
    A = array( [ [1,2,3], [4,5,6] ] )
    A.nbytes
    24

But, what about dictionaries?
I saw lot of answers proposing to use pysize or heapy. An easy answer is given by Torsten Marek in this link: https://stackoverflow.com/questions/110259/python-memory-profiler, but I haven&#39;t a clear interpretation about the output because the number of bytes didn&#39;t match.

Pysize seems to be more complicated and I haven&#39;t a clear idea about how to use it yet.

Given the simplicity of size calculation that I want to perform (no classes nor complex structures), any idea about a easy way to get a approximate estimation of memory usage of this kind of objects?


Kind regards.

How to know bytes size of python object like arrays and dictionaries? - The simple way

Is it possible to get the object property name as a string

    person = {};
    person.first_name = &#39;Jack&#39;;
    person.last_name = &#39;Trades&#39;;
    person.address = {};
    person.address.street = &#39;Factory 1&#39;;
    person.address.country = &#39;USA&#39;;

I&#39;d like to use it like this:

    var pn = propName( person.address.country ); // should return &#39;country&#39; or &#39;person.address.country&#39;
    var pn = propName( person.first_name );      // should return &#39;first_name&#39; or &#39;person.first_name&#39;


**NOTE**: this code is exactly what I&#39;m looking for. I understand it sounds even stupid, but it&#39;s not.

This is what I want to do with it.

HTML
    &lt;input type=&quot;text&quot; value=&quot;Jack&quot; id=&quot;id_first_name &quot;/&gt;

    person = {};
    person.id_first_name = &#39;Jack&#39;;
    person.id_last_name = &#39;Trades&#39;;
    person.address = {};
    person.address.id_address = &#39;Factory 1&#39;;
    person.address.id_country = &#39;USA&#39;;


    extPort.postMessage
    (
      {
        message : MSG_ACTION,
        propName( person.first_name ): person.first_name
      }
    };

----------------------**ANSWER**-----------------------

Got it thanks to ibu. He pointed the right way and I used a recursive function

    var res = &#39;&#39;;
    
    function propName(prop, value) {
    	for (var i in prop) {
    		if (typeof prop[i] == &#39;object&#39;) {
    			if (propName(prop[i], value)) {
    				return res;
    			}
    		} else {
    			if (prop[i] == value) {
    				res = i;
    				return res;
    			}
    		}
    	}
    	return undefined;
    }
    
    var pn = propName(person, person.first_name); // returns &#39;first_name&#39;
    var pn = propName(person, person.address.country); // returns &#39;country&#39;

DEMO: http://jsbin.com/iyabal/1/edit

Content Type	Original Author	Original Content on Stackoverflow
Question	chris	View Question on Stackoverflow
Solution 1 - Javascript	bhovhannes	View Answer on Stackoverflow
Solution 2 - Javascript	Doink	View Answer on Stackoverflow
Solution 3 - Javascript	VisioN	View Answer on Stackoverflow

javascript, is there an isObject function like isArray?

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Why does the C# compiler not fault code where a static method calls an instance method?

What does an exclamation mark mean in the Swift language?

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