There is no reason not to use `typeof`.

Not only is it faster but the [ECMAScript specification][1] ensures that all functions have a type of &quot;function&quot; and that only functions can have a type of &quot;function&quot; :


![enter image description here][2]

This operator was specifically designed to get the type of a value, so why not use it ?

  [1]: http://es5.github.io/#x11.4.3
  [2]: http://i.stack.imgur.com/9AUle.png

Firstly, Underscore doesn&#39;t use that implementation anymore. It optimizes to `typeof` unless `typeof /./` returns `function`, as it did atleast in [older versions of Chrome](https://stackoverflow.com/a/5054396/320615)


You can find this in the source code: http://underscorejs.org/underscore.js

    // Optimize `isFunction` if appropriate.
      if (typeof (/./) !== &#39;function&#39;) {
        _.isFunction = function(obj) {
          return typeof obj === &#39;function&#39;;
        };
      }

New jsperf: http://jsperf.com/comparing-underscore-js-isfunction-with-typeof-function/3

It still shows quite a performance hit in FF (but MUCH less than the naive implementation you posted in the question), which is due to the overhead of a function call vs just inlining code.

I am using Jekyll as a static generator for a website (not a blog), and I want to have an automatically generated list of all pages on my index page. Specifically, I want to have different categories and list all articles in each category separately. [Here&#39;s](http://www.gwern.net/) an example of what I&#39;m describing, if you&#39;re having trouble following. Is there any way to do this in Jekyll (e.g. GitHub pages)? I&#39;ve seen the [variables documentation page](http://jekyllrb.com/docs/variables/) but that seems specific to the blog post format.

Generating a list of pages (not posts) in a given category

Most of our team consists of java developers and therefore the whole build / deployment / dependency management system is built on top of maven. We use CI so every build process runs unit test (w. karma and phantomJS for the frontend, and jasmine-node for the backend). I&#39;ve managed to configure a karma maven plugin for this purpose.

**This does not solve the issue of downloading node.js dependencies from package.json on build.** I need to deploy my node.js / express app in existing environment, so the perfect scenario would be:

1. pull from the repo (done automatically with maven build)
2. `npm install` (that is - downloading dependencies from node package registry)
3. running tests

I was trying to find a nodejs package for maven, but to be honest - as a node.js developer I do not feel very confident when it comes to choosing the right tools, since I&#39;m not able to distinguish a bad maven plugin from a decent one.

Maybe using a shell plugin and invoking `npm install` from the terminal is a better choice?

What&#39;s your opinion?

How to deploy a node.js app with maven?

I think it might be only performance case - http://jsperf.com/comparing-underscore-js-isfunction-with-typeof-function/2

And seems that ``typeof`` is faster.. so my question is - which is more appropriate to use?

_.isFunction(a) vs. typeof a === &#39;function&#39;? javascript

<p>I think it might be only performance case - <a href="http://jsperf.com/comparing-underscore-js-isfunction-with-typeof-function/2" target="_blank" rel="noopener noreferrer">http://jsperf.com/comparing-underscore-js-isfunction-with-typeof-function/2</a></p>
<p>And seems that <code>typeof</code> is faster.. so my question is - which is more appropriate to use?</p>


In JavaScript, I need to know if all object items are set to true.

If I have the following object:

    var myObj = {title:true, name:true, email:false};

I could write something like this :   

     if(myObj.title &amp;&amp; myObj.name &amp;&amp; myObj.email){
     /*Some code */
    };

But I am looking for the simplest way to write it. eg :

    if(myObj all is true){
    /*Some code */
    };

I might have another object with 10-20 items inside it, and will need to know if all are true.



How to know if all javascript object values are true?

I realise there is a lot of topics on this subject but I believe this one is different:

The goal is to get an value from an array on a random location then delete this value.

I use this part by John Resig (the creator of jQuery) to remove an element but it doesn&#39;t seem to listen to the location I give it

	Array.prototype.remove = function(from, to) {
	var rest = this.slice((to || from) + 1 || this.length);
	this.length = from &lt; 0 ? this.length + from : from;
	return this.push.apply(this, rest);
	};

this is how I use it
											
	var elements = [&#39;#1&#39;,&#39;#2&#39;,&#39;#3&#39;,&#39;#4&#39;]
	var R1 = Math.floor(Math.random() * elements.length),
	E1 = elements.slice(R1,1)
	elements.remove(R1)
	var R2 = Math.floor(Math.random() * elements.length),
	E2 = elements.slice(R2,1)
	elements.remove(R2)
	var R3 = Math.floor(Math.random() * elements.length),
	E3 = elements.slice(R3,1)
	elements.remove(R3)
	var R4 = Math.floor(Math.random() * elements.length),
	E4 = elements.slice(R4,1)

The problem is the remove function, it doesn&#39;t work when removing a object on a specific location I believe.

Removing value from array on specific location

I have the following JavaScript object:

    var obj = {
        &quot;key1&quot; : val,
        &quot;key2&quot; : val,
        &quot;key3&quot; : val
    }

Is there a way to check if a key exists in the array, similar to this?

    testArray = jQuery.inArray(&quot;key1&quot;, obj);

does not work.

Do I have to iterate through the obj like this?

    jQuery.each(obj, function(key,val)){}

Checking if a key exists in a JS object

I&#39;m trying to learn grunt. When I run npm init, I get a prompt in the process of creating a package.json file that asks for &quot;test command&quot; - I&#39;m not sure how to utilize this, or what it&#39;s expecting. It doesn&#39;t seem to be well documented. If I leave it blank, I get this in the resulting package.json file:

    &quot;scripts&quot;: {
        //&quot;test&quot;: &quot;echo \&quot;Error: no test specified\&quot; &amp;&amp; exit 1&quot;
      },

Can anybody shed some light on how to set up a test script?

what does grunt &quot;test command&quot; do on npm init

I&#39;m trying to draw with the mouse over a HTML5 canvas, but the only way that it seems to work well is if the canvas is in the position 0,0 (upper left corner) if I change the canvas position, for some reason it doesn&#39;t draw like it should. Here is my code.

     function createImageOnCanvas(imageId){
        document.getElementById(&quot;imgCanvas&quot;).style.display = &quot;block&quot;;
        document.getElementById(&quot;images&quot;).style.overflowY= &quot;hidden&quot;;
        var canvas = document.getElementById(&quot;imgCanvas&quot;);
        var context = canvas.getContext(&quot;2d&quot;);
        var img = new Image(300,300);
        img.src = document.getElementById(imageId).src;
        context.drawImage(img, (0),(0));
    }

    function draw(e){
        var canvas = document.getElementById(&quot;imgCanvas&quot;);
        var context = canvas.getContext(&quot;2d&quot;);
        posx = e.clientX;
        posy = e.clientY;
        context.fillStyle = &quot;#000000&quot;;
        context.fillRect (posx, posy, 4, 4);
    }

**The HTML part**

     &lt;body&gt;
     &lt;div id=&quot;images&quot;&gt;
     &lt;/div&gt;
     &lt;canvas onmousemove=&quot;draw(event)&quot; style=&quot;margin:0;padding:0;&quot; id=&quot;imgCanvas&quot;
              class=&quot;canvasView&quot; width=&quot;250&quot; height=&quot;250&quot;&gt;&lt;/canvas&gt; 


I have read there&#39;s a way of creating a simple function in JavaScript to get the right position, but I have no idea about how to do it. 

Real mouse position in canvas

I&#39;ve got a in if-elif-elif-else statement in which 99% of the time, the else statement is executed:

    if something == &#39;this&#39;:
        doThis()
    elif something == &#39;that&#39;:
        doThat()
    elif something == &#39;there&#39;:
        doThere()
    else:
        doThisMostOfTheTime()

This construct is done **a lot**, but since it goes over every condition before it hits the else I have the feeling this is not very efficient, let alone Pythonic. On the other hand, it does need to know if any of those conditions are met, so it should test it anyway.

Does anybody know if and how this could be done more efficiently or is this simply the best possible way to do it?

Most efficient way of making an if-elif-elif-else statement when the else is done the most?

This is the configuration of my test plan thread properties:
		
	Number of Threads (users): 100
	Ramp-up Period (in seconds): 10
	Loop Count : Forever
	Delay thread creation until needed: No
	Scheduler: No

I ran the test overnight with the total duration of 14 hours and 7 minutes (approximately 50820 seconds). After loading the jtl file, The number of samples shown in summary report is 1050975. I tried to compute but I can&#39;t understand how it came up with that many sample.

If Ramp-up Period is the time taken by JMeter to create the number of threads per iteration and if the duration of the test is 50820 seconds, then I should have 508200 samples only ( 50820/10 * 100 ). I do not know how or if Loop Count affects this.

JMeter understanding ramp-up

I have a model with possibly thousands of objects. I was wondering what would be the most efficient way of storing them and retrieving a single object once I have it&#39;s id. The id&#39;s are long numbers.

So these are the 2 options I was thinking about. in option one it&#39;s a simple array with an incrementing index. in option 2 it&#39;s an associative array and maybe an object, if it makes a difference. My question is which one is more efficient, when I mostly need to retrieve a single object, but also sometimes loop through them and sort.

Option one with non associative array:

    var a = [{id: 29938, name: &#39;name1&#39;},
             {id: 32994, name: &#39;name1&#39;}];
    function getObject(id) {
    	for (var i=0; i &lt; a.length; i++) {
    		if (a[i].id == id) 
    			return a[i];
    	}
    }
    
Option two with associative array:

    var a = [];  // maybe {} makes a difference?
    a[29938] = {id: 29938, name: &#39;name1&#39;};
    a[32994] = {id: 32994, name: &#39;name1&#39;};
    function getObject(id) {
    	return a[id];
    }

**Update:**

OK, I get that using an array in the second option is out of the question. So the declaration line the second option should really be: `var a = {};` and the only question is: what is performing better in retrieving an object with a given id: an array or an object where the id is the key.

and also, will the answer change if i will have to sort the list many times?

Array vs. Object efficiency in JavaScript

I read everywhere that ternary operator is supposed to be faster than, or at least the same as, its equivalent `if`-`else` block.

However, I did the following test and found out it&#39;s not the case:

    Random r = new Random();
    int[] array = new int[20000000];
    for(int i = 0; i &lt; array.Length; i++)
    {
        array[i] = r.Next(int.MinValue, int.MaxValue);
    }
    Array.Sort(array);

    long value = 0;
    DateTime begin = DateTime.UtcNow;

    foreach (int i in array)
    {
        if (i &gt; 0)
        {
            value += 2;
        }
        else
        {
            value += 3;
        }
        // if-else block above takes on average 85 ms

        // OR I can use a ternary operator:
        // value += i &gt; 0 ? 2 : 3; // takes 157 ms
    }
    DateTime end = DateTime.UtcNow;
    MessageBox.Show(&quot;Measured time: &quot; + (end-begin).TotalMilliseconds + &quot; ms.\r\nResult = &quot; + value.ToString());

My computer took 85 ms to run the code above. But if I comment out the `if`-`else` chunk, and uncomment the ternary operator line, it will take about 157 ms.

Why is this happening?

Ternary operator is twice as slow as an if-else block?

I mean: how can I measure time my CPU spent on function execution and wall clock time it takes to run my function? (Im interested in Linux/Windows and both x86 and x86_64). See what I want to do (Im using C++ here but I would prefer C solution):

    int startcputime, endcputime, wcts, wcte;
    
    startcputime = cputime();
    function(args);
    endcputime = cputime();
    
    std::cout &lt;&lt; &quot;it took &quot; &lt;&lt; endcputime - startcputime &lt;&lt; &quot; s of CPU to execute this\n&quot;;
    
    wcts = wallclocktime();
    function(args);
    wcte = wallclocktime();
    
    std::cout &lt;&lt; &quot;it took &quot; &lt;&lt; wcte - wcts &lt;&lt; &quot; s of real time to execute this\n&quot;;

**Another important question: is this type of time measuring architecture independent or not?**

How can I measure CPU time and wall clock time on both Linux/Windows?

Here is my code for javascript for this simple task:

  

1. **Remove** the element if it exists in an array.&lt;br/&gt; 
2. **Add** the element if it is not in an array.


		if(_.contains(this.types,type_id)){
			var index = this.types.indexOf(type_id);
			this.types.splice(index,1);
		}
        else{
			this.types.push(type_id);
		}

Is there a more efficient way to do this?			


How to toggle an element in array using JavaScript?

I would like to filter a collection using array of property value. Given an array of IDs, return objects with matching IDs. Is there any shortcut method using `lodash`/`underscore`?

&lt;!-- language: lang-js --&gt;

    var collections = [{ id: 1, name: &#39;xyz&#39; },
                       { id: 2,  name: &#39;ds&#39; },
                       { id: 3,  name: &#39;rtrt&#39; },
                       { id: 4,  name: &#39;nhf&#39; },
                       { id: 5,  name: &#39;qwe&#39; }];
    var ids = [1,3,4];

    // This works, but any better way?

    var filtered = _.select(collections, function(c){    
        return ids.indexOf(c.id) != -1
    });

lodash Filter collection using array of values

I have a web page that is part of a ASP.NET web site running on Azure.  It&#39;s run fine for quite a while now.  Out of the blue, I am suddenly having a problem with the browser trying to download a &quot;.map&quot; for Underscore.js.  I did some reading and apparently JQuery creates &quot;.map&quot; files as debugging aids for Javascript source files (&quot;.js&quot;).  However, if I look at the Scripts directory for my web site I see that this only happens for some JQuery source files and not all and I am not sure what the pattern is.

However, why would the browser be trying to load a &quot;map&quot; file for Underscore.js which is not part of JQuery?  Also, why would this suddenly start happening?  I added Underscore.js to the web page quite some time ago and never had this problem before.  

The exact error I get when I look in the Chrome Debugger Console tab is:

GET http://myazureapp.cloudapp.net/Scripts/underscore-min.map 404 (Not Found) Scripts/underscore-min.map:1

Missing Javascript &quot;.map&quot; file for Underscore.js when loading ASP.NET web page

The code in node.js is simple enough.

    _.each(users, function(u, index) {
      if (u.superUser === false) {
        //return false would break
        //continue?
      }
      //Some code
    });

My question is how can I continue to next index without executing &quot;Some code&quot; if superUser is set to false?

PS: I know an else condition would solve the problem. Still curious to know the answer.

How to &#39;continue&#39; inside a each loop : underscore, node.js

The ``map`` function in underscore.js, if called with a javascript object, returns an array of values mapped from the object&#39;s values.

    _.map({one: 1, two: 2, three: 3}, function(num, key){ return num * 3; });
    =&gt; [3, 6, 9]

is there a way to make it preserve the keys? ie, I want a function that returns

    {one: 3, two: 6, three: 9}

Map over object preserving keys

Getting the classname of an object as `String` using:

    object_getClassName(myViewController)

returns something like this:

    _TtC5AppName22CalendarViewController

I am looking for the *pure* version: `&quot;CalendarViewController&quot;`. How do I get a *cleaned up* string of the class name instead? 

I found some attempts of questions about this but not an actual answer. Is it not possible at all?

Get class name of object as string in Swift

Explain to me what `keyof typeof` means in TypeScript

Example:

    enum ColorsEnum {
        white = &#39;#ffffff&#39;,
        black = &#39;#000000&#39;,
    }
    
    type Colors = keyof typeof ColorsEnum;

The last row is equivalent to:

    type Colors = &quot;white&quot; | &quot;black&quot;

But how does it work?

I would expect `typeof ColorsEnum` to return something like `&quot;Object&quot;` and then `keyof &quot;Object&quot;` to not do anything interesting. But I am obviously wrong.

What does &quot;keyof typeof&quot; mean in TypeScript?

According to [MDN&#39;s documentation on `undefined`][1]:

&gt; In modern browsers (JavaScript 1.8.5 / Firefox 4+), undefined is a non-configurable, non-writable property per the ECMAScript 5 specification. Even when this is not the case, avoid overriding it.

One of the property attributes of *undefined* is that is not writable.

But if I do:

&lt;!-- begin snippet: js hide: false console: true babel: false --&gt;

&lt;!-- language: lang-js --&gt;

    var undefined = &#39;hello&#39;;
    var test = undefined;
    console.log(typeof test);
    //string

&lt;!-- end snippet --&gt;

Does that mean that I can overwrite the value of `undefined`? What happens if someone does that? Should JavaScript warn about that?

  [1]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/undefined







Content Type	Original Author	Original Content on Stackoverflow
Question	Kosmetika	View Question on Stackoverflow
Solution 1 - Javascript	Denys Séguret	View Answer on Stackoverflow
Solution 2 - Javascript	Dogbert	View Answer on Stackoverflow

_.isFunction(a) vs. typeof a === 'function'? javascript

Javascript Problem Overview

Javascript Solutions

Solution 1 - Javascript

Solution 2 - Javascript

How to deploy a node.js app with maven?

Generating a list of pages (not posts) in a given category

Attributions