While checking if there is a value for a property in an object, I was using if(prop in object) return object[prop] else object[prop] = x (x is some variable outside of this question) to determine if an entry has been made into the object. Should I just use if(object[prop]), because if the property doesn't exist, it will return undefined? Is using the in operator just as fast? The only pitfall caused by changing to check the value is if the value if null, 0, -0, false, or NaN, it will return false when I want a falsy value, is there anything else I should watch out for?
How do I check if an object has a specific property in JavaScript?  Consider:  x = {'key': 1}; if ( x.hasOwnProperty('key') ) {     //Do this }   Is that the best way to do it?
In which countries are the visitor's first name and last name compulsory? My name consists of just a first name and no surname.  Will there be a problem regarding my name in the country I visit with a tourist or employment visa? Are there countries in the world where this might be a problem? How to resolve ambiguous column names when retrieving results? What is the remainder of $\,3^{3^{3^{\:\!\phantom{}^{.^{.^.}}}}}\!\!\!$ divided by $46$?  The level of powers is $2020$.  First there is no parenthesis so it means 3 power of 3 which is also power 3 and so on 2020 times  Second I think that we can use Fermat's Little Theorem but I don't know how, and maybe there is a better way. How do you handle uneven tiles while rendering a tile map? Here is what I want to do with my tile map that I am unsure of. As you can see the top walls are way larger then the bottom and side ones (this is also an issue with my corners which are odd shapes [more like an L then a square] as well as larger then the 40x40px that my current tiles are).    I have also attached the tile sheet I am using for the tiles to show you what the corners and tops look like compared to the rest of the tiles.  What I’m thinking is I might be able to just draw them using the same array I have if I use the tiles width and height instead of a set WxH? I dont know how well this will work, but were the blocks that will have different values will be blocks the player/NPCs can’t step on then it may not be an issue, again I’m not even sure if that is a viable solution.  My code in case you want to see how I'm currently handling it:  (pastebin) (edit:im not handling it, meant how I'm currently doing the map)  tl;dr - how can I take take my 2d looking tile map and change it to have different size tiles? or is there a better way to do what I am trying to do? Is there a name of a method that I should be looking for while googling? How do I login as root? I can't connect to a friend's Minecraft server, but none of the usual culprits seem to be the problem How to implement a single instance Java application? sum numbers in different lines in shell i have 8000 lines similar to this   &lt;Flow flowId="1" timeFirstTxPacket="+0.0ns" timeFirstRxPacket="+924100.0ns" timeLastTxPacket="+199984927558.0ns" timeLastRxPacket="+199675473275.0ns" delaySum="+2287566662167.0ns" jitterSum="+65280162191.0ns" lastDelay="+3511349483.0ns" txBytes="161956" rxBytes="116536" txPackets="3125" rxPackets="2251" lostPackets="640" timesForwarded="0"&gt;   and what i need to do is summing rxPackets in each line together and txPackets too   i mean total sum of them in 8000 lines  thanks in advance  &lt;Flow flowId="1" timeFirstTxPacket="+0.0ns" timeFirstRxPacket="+924100.0ns" timeLastTxPacket="+199984927558.0ns" timeLastRxPacket="+199675473275.0ns" delaySum="+2287566662167.0ns" jitterSum="+65280162191.0ns" lastDelay="+3511349483.0ns" txBytes="161956" rxBytes="116536" txPackets="3125" rxPackets="2251" lostPackets="640" timesForwarded="0"&gt;  &lt;Flow flowId="2" timeFirstTxPacket="+3000000.0ns" timeFirstRxPacket="+3254190.0ns" timeLastTxPacket="+199988489445.0ns" timeLastRxPacket="+199631899307.0ns" delaySum="+12081144328484.0ns" jitterSum="+105606015634.0ns" lastDelay="+9407845452.0ns" txBytes="251896" rxBytes="124840" txPackets="4867" rxPackets="2413" lostPackets="1757" timesForwarded="0"&gt;  &lt;Flow flowId="3" timeFirstTxPacket="+4000000.0ns" timeFirstRxPacket="+4254098.0ns" timeLastTxPacket="+199971756470.0ns" timeLastRxPacket="+198959480315.0ns" delaySum="+5150205600987.0ns" jitterSum="+74009967633.0ns" lastDelay="+9862217799.0ns" txBytes="163044" rxBytes="90532" txPackets="3150" rxPackets="1751" lostPackets="1013" timesForwarded="0"&gt; I'm rotating an object on two axes, so why does it keep twisting around the third axis? I see questions come up quite often that have this underlying issue, but they're all caught up in the particulars of a given feature or tool. Here's an attempt to create a canonical answer we can refer users to when this comes up - with lots of animated examples! :)    Let's say we're making a first-person camera. The basic idea is it should yaw to look left &amp; right, and pitch to look up &amp; down. So we write a bit of code like this (using Unity as an example):  void Update() {     float speed = lookSpeed * Time.deltaTime;      // Yaw around the y axis using the player's horizontal input.             transform.Rotate(0f, Input.GetAxis("Horizontal") * speed, 0f);      // Pitch around the x axis using the player's vertical input.     transform.Rotate(-Input.GetAxis("Vertical") * speed,  0f, 0f); }   or maybe  // Construct a quaternion or a matrix representing incremental camera rotation. Quaternion rotation = Quaternion.Euler(                         -Input.GetAxis("Vertical") * speed,                          Input.GetAxis("Horizontal") * speed,                          0);  // Fold this change into the camera's current rotation. transform.rotation *= rotation;   And it mostly works, but over time the view starts to get crooked. The camera seems to be turning on its roll axis (z) even though we only told it to rotate on the x and y!    This can also happen if we're trying to manipulate an object in front of the camera - say it's a globe we want to turn to look around:    The same problem - after a while the North pole starts to wander away to the left or right. We're giving input on two axes but we're getting this confusing rotation on a third. And it happens whether we apply all our rotations around the object's local axes or the world's global axes.  In many engines you'll also see this in the inspector - rotate the object in the world, and suddenly numbers change on an axis we didn't even touch!    So, is this an engine bug? How do we tell the program we don't want it adding extra rotation?  Does it have something to do with Euler angles? Should I use Quaternions or Rotation Matrices or Basis Vectors instead? Proving that a normal, abelian subgroup of G is in the center of G if |G/N| and |Aut(N)| are relatively prime. How to partition for Windows/Ubuntu dual boot on same SSD I have a 500GB SSD in which i would like to have both Windows and Ubuntu. My plan is to have something similar to this: Windows 8.1 and ubuntu 14.04 Uefi boot   an efi partition (created by windows installer) which will have Grub as bootloader 150GB ntfs for Windows 15GB ext4 for Ubuntu (root) 35GB ext4 for Ubuntu (home) ~8-16GB swap for Ubuntu (I have 16GB RAM) ~284-292GB ntfs for Data shared for both Windows and Ubuntu   My current setup is   200GB ntfs Windows 300GB ntfs for Data   I plan to shrink both the Windows and the data partiton in order to achieve my desired plan.  My questions:   Does the order of partitions matter? Does it matter if the ubuntu partitions are not at the end/beggining of the drive? Does the swap partition behaves better if its the last/first partition? Can I use the shared NTFS Data partition between windows and ubuntu without encountering problems? Do I have enough space for my ubuntu /home partition (thinking that I'll have access to the ntfs shared partition)?   Edit: Laptop, Asus N56jr, i7, 16Gb Ram, SSD samsung 850 evo 500gb  Windows 8.1 and Ubuntu 14.04 p-value approach - clarify teacher's solution? So I have a question with my teacher's solution below and I'm confused about one of the steps in their solution. I would appreciate some clarification.  Two brands of coffee were compared. Two independent random samples of 50 people each were asked to taste either Brand A or Brand B coffee, and indicate whether they liked it or not. Eighty four percent of the people who tasted Brand A liked it; the analogous sample proportion for Brand B was ninety percent.   (A) At α = 0.01, is there a significant difference in the proportions of individuals who like the two coffees? Use the p-value approach.   So I circled in blue a step where I'm confused about in the teacher's solution. I don't understand why P(Z&lt;-0.89) = 0.2061.   On the z-score table -0.89 is equal to 0.1867 so shouldn't it be that value instead? where did 0.2061 come from? Is it possible that the teacher made an error or am I not understanding something? A local IP address (RFC 1918) on my network that is not … local I've noticed an IP address today on my network (192.168.15.1) which when visited actually goes to a page that has a router webconfig page (Not my router)  The puzzling thing is that i tried traceroute 192.168.15.1 which said that the distance between me and that host is 9 hops, whereas the distance between me and any other computer on my home network is 2 hops away (My computer --> Router --> Host)   Can someone please explain what's going on here ?  tracert output:  Tracing route to 192.168.15.1 over a maximum of 30 hops    1    &lt;1 ms    &lt;1 ms    &lt;1 ms  192.168.1.1   2    47 ms    51 ms    49 ms  [163.121.171.123]   3     *        *        *     Request timed out.   4   128 ms     *        *     163.121.211.134.dnet.net [163.121.211.134 ]   5     *      134 ms   126 ms  10.37.242.18   6    94 ms    90 ms    95 ms  10.35.2.157   7   178 ms   254 ms   206 ms  10.32.8.107   8    85 ms    57 ms   318 ms  10.35.0.186   9   215 ms   241 ms   230 ms  192.168.15.1  Trace complete. A word for "intimate friends" without any kind of romance? I'm looking for a word to describe that a particular situation where two people (a man and a woman) are probably the best of friends but have no romantic inclinations towards each other. They may invade each others thoughts periodically but aren't really in a relationship per se. What would be a good word to describe this?  I'm aware of "platonic" but am wondering if there is another word? I am asked to fill the genotypes in the spaces provided but looks like I am aving a little bit of trouble. can anyone help? thanks in advance! Artinian affine $K$-algebra Prove that $C\exp(x)$ is the only set of functions for which $f(x) = f'(x)$ I was wondering on the following and I probably know the answer already: NO. Is there another number with similar properties as $e$? So that the derivative of $\exp(x)$ is the same as the function itself. I can guess that it's probably not, because otherwise $e$ wouldn't be that special, but is there any proof of it? I am attempting to install Ubuntu on a box which was previously running Windows 7.  I have also experienced the dreaded "Unable to install GRUB" error.  I am not attempting to dual boot. I have previously run a Windows boot disk and removed all existing partitions.  If I run the Ubuntu 12.04 install CD and click install after the config screens, I get the error   Executing 'grub-install /dev/sda' failed. This is a fatal error. (It is the same error as this question: )  All the questions I've read while looking for a solution are related to dual boot.  I'm not interested in dual boot, I'm after a clean out the box Ubuntu install. How can I achieve this?  (For my sanity, please use very simple instructions when responding. I don't claim to have any talent either for linux or as a sysadmin)    Additional details copied from comments dated: 2012-05-29 ~15:19Z  After booting from the CD, clicking Try Ubuntu, and then sudo fdisk /dev/sda I get fdisk: unable to seek on /dev/sda: Invalid argument  sudo fdisk /dev/sdb gives   Device contains neither a valid DOS partiion table, nor Sun, SGI or OSF disklabel.  Building a new DOS disklabel with disk identifier 0x15228d1d.  Changes will remain in memory only until you decide to write them.  After that of course, the previous content won't be recoverable.  Warning: invalid flag 0x0000 of partition table 4 will be corrected by w(rite).  Command (m for help):   I should add the Live CD desktop is graphically bad. I've got missing parts of programs and the terminal occasionally reflects to the bottom of the screen. But I can't imagine this is related. Rows to column conversion of file Suppose I have a file:  File1:   PAPER  TEAM  MANISH NISHA GARIMA JYOUTI ........etc    File2 I want:  PAPER     TEAM MANISH NISHA GARIMA     JYOUTI   Rows to column conversion of File1. Why is scale factor inversely proprotional to temperature? In all lectures, books and papers I have read about, the scale factor of the universe is inversely proportional to temperature  $$a \propto \frac{1}{T}$$  What is the reasoning behind this relation?  People did mention stretching of wavelength proportional to scale factor and wavelength being inversely proportional to temperature by Wein's law, but somehow this argument doesn't seem convincing to me. How did we initially come about to this relation?