if (foo) {     // code to run if foo exists     }   results in Uncaught ReferenceError: foo is not defined  So how am i supposed to check if foo exists?
How to check whether a JavaScript variable defined in cross-browser way?  I ran into this problem when writing some JavaScript utilizing FireBug logging. I wrote some code like below:  function profileRun(f) {     // f: functions to be profiled     console.profile(f.constructor);     f();     console.profileEnd(f.constructor); }   It works fine in FireFox/FireBug, but it reports error in IE8 RC1. So, I'd like to do some checking whether console variable exists in the execution environment.  Below code works fine in FireFox, but not in IE8 RC1.   function profileRun(f) {     if (console != undefined) {         console.profile(f.constructor);     }      f();      if (console != undefined) {         console.profileEnd(f.constructor);     } }   However, if I do it this way. It works in IE8 RC1. Why?   function profileRun(f) {     if (window.console != undefined) {         console.profile(f.constructor);     }      f();      if (window.console != undefined) {         console.profileEnd(f.constructor);     } }   Is there any cross-browser way to check it?
How does IPv4 Subnetting Work? I'm absolutely new to Linux. I would like to know how to install Ubuntu alongside the pre-installed Windows 8+ OS.  Should I do it with Wubi, or through the Live USB/DVD?  What steps do I need to take to correctly install Ubuntu? Is it possible to win in Don't Starve? I would like to know if it's possible to win in Don't Starve? Or is it just the matter of how long until you die? The adverb "quite" has the following meanings :     1: wholly, completely ("not quite   finished")      2: to an extreme : positively "quite   sure" —often used as an intensifier   with a "quite a swell guy" "quite a   beauty"      3: to a considerable extent : rather   ("quite near")   My understanding is that #1 and #2 conflict with #3. For example, when you say "She's quite right", do you mean "She's completely right" or "To a considerable extent, she's right"? Notice that in the latter case you're not saying that she is completely right.  Another example is "I'm quite sure". Does it necessarily mean "I'm completely sure"?   Does the word really have conflicting meanings that can possibly cause ambiguity? Or am I missing something? Ubuntu 16.04 slow boot (apt-daily.service) My boot is horribly slow, and I don't know why.  $ systemd-analyze  Startup finished in 10.975s (kernel) + 49.732s (userspace) = 1min 708ms $ systemd-analyze blame           34.971s apt-daily.service          20.590s snapd.refresh.service          17.113s grub-common.service          16.033s apport.service          16.027s networking.service          15.894s ondemand.service          15.860s irqbalance.service          15.655s speech-dispatcher.service          11.695s ModemManager.service           9.772s accounts-daemon.service           8.626s NetworkManager-wait-online.service           8.058s systemd-logind.service           8.053s bluetooth.service           7.944s gpu-manager.service           7.896s alsa-restore.service           7.892s pppd-dns.service           7.882s rsyslog.service           7.860s avahi-daemon.service           7.844s dev-sda1.device           7.842s systemd-user-sessions.service           7.648s lightdm.service           7.610s teamviewerd.service           6.445s apparmor.service   Also, during boot-up, I see a message that says something like:  device descriptor read/all, error -62 ata1 softreset failed (device not ready) #most of the times error loading journal #(sometimes) Test WP failed, assume Write Enabled Asking for cache data failed     #most of the times Assuming drive cache: write through   apt-daily.service slows the boot the most. Any idea on how to tackle that?  I have Ubuntu MATE 16.04. If $E/F$ is algebraic and every $f\in F[X]$ has a root in $E$, why is $E$ algebraically closed? FM transmitter design? I stumbled across a relatively simple FM radio transmitter online.    Credit:   I wanted to understand how it works (it is called "super simple" on the website), but several hours I have nothing but a vague understanding.   I believe R2, L1, C3 form an oscillator, and then the transistor Q1 is used to modulate the signal. C1 would just be used to remove any DC offset. However, this leaves R1, C2, C4, C5, and R3 and,  for these components,  I have no clue what they do.   Could someone please explain how this "super simple" transmitter works? How does gravity work underground? Would the effect of gravity on me change if I were to dig a very deep hole and stand in it? If so, how would it change? Am I more likely to be pulled downwards, or pulled towards the edges of the hole? If there would be no change, why not? Why do "stripes" appear on raster? I am reprojecting a SRTM 3 arc-second raster file from WGS84 geographic coordinate system, to projected coordinate system which is using Azimuthal Equidistant projection:  gdalwarp -s_srs EPSG:4326 -t_srs "+proj=merc +lat_ts=40.81266 +lon_0=14.414252" -r near -of GTiff C:/vesuvius2_wgs84.tif C:/vesuvius2_aeqd.tif   I attached the initial raster file in here ().  The issue is that if I use the Nearest neighbor resampling method (-r near), some sort of "stripes" appear on terrain once I reproject the file to Azimuthal Equidistant projection. Here is the how the reprojected raster looks like:    And here is its 3d representation:    Interestingly similar "stripes" appear in both direction if I reproject the initial raster to UTM:  gdalwarp -s_srs EPSG:4326 -t_srs EPSG:32633 -r near -of GTiff C:/vesuvius2_wgs84.tif C:/vesuvius2_epsg32633.tif   The "stripes" go away when I use Bilinear or Cubic resampling methods (-r bilinear, -r cubic) instead of the Nearest Neighbor one.  Why do these "stripes" appear when Nearest Neighbor resampling method is used? Is the sign of principal components meaningless? Why my U.S. B1 Visa got refused under 214 (b)? Make rigid body collide with hair particles I've searched for multiple forums for this questions and have seen different answers but so far, nothing have worked yet even from the ones I've seen here.  I want to extract a single file from a tar to a different directory.  I've tried this:  tar xvf file.tar -C /home/dir/ filename   or this:  tar -x filename -f file.tar -C /home/dir   But got these errors respectively:  x filename, 14826 bytes, 29 media blocks. File -C not present in the archive. File /home/dir not present in the archive.   and:  tar: /dev/rmt0: A file or directory in the path name does not exist.   The first extracted the file but in the same directory, not to the folder I wanted. I am trying to (partially) reproduce the algorithm displayed in Figure 4 from   My problem is with the multi-line conditions present in the "IFs". I want them to be indented, but \Indp does not seem to take effect if a new line \\ is not present in the same line.  This is what I tried:  \begin{algorithm}[htb]     \SetAlgoNoLine%     \SetNoFillComment     \SetKwIF{If}{ElseIf}{Else}{if}{:}{elif}{else:}{}%      \If{(SYNs from both hosts and \\             \Indp SYNs in earliest NFs of both hosts and \\             \Indp hosts' earliest packets differ)}{         Host with earliest NF is originator      }     \If{(SYN only from one host and \\         \Indp SYN is in connection's earliest NF)}{     Host is originator     }     \If{one host uses port 20 (ftp-data)}{     Host is originator     }     \If{only one host uses a well-known port}{     Host is responder     }     \If{start of hosts' first packets differ}{     Host with earliest NF is originator     }     Arbitrarily choose originator     \caption{Pseudo code for determining connection server side}     \label{algo:serverside2} \end{algorithm}   For instance, the line "SYNs in earliest NFs of both hosts and" is indented correctly, but "hosts' earliest packets differ" is not. Change folder permissions and ownership I would like the user to have full rights on this folder (as well as all sub-directories and files in it):  ~/.blabla   currently owned by root.  I have found numerous posts (in this forum and elsewhere) on how to do this for files but I can't find a way to do it for whole folders. How can I tell how long (more or less) it will take me to complete a game? I'm going down my huge backlog of unplayed Steam games and I'm thinking the best way to tackle the list is to go through the shortest games first and then concentrate on the 20+ hour ones. I'm wondering if there's a website or something else that has an estimated amount of gameplay time for games.   Is there anything like that? What happens when a familiar from the Find Familiar spell "dies"? Can a Stack Exchange association bonus be lost? I recently hit 200 rep on Stack Overflow and got a big 100 rep bonus. Most know this as the 'association bonus'.  If I offer a bounty of 50 points and thereby lessen my 'base' score, do I lose that association bonus?  What if I offer a 150 point bounty and then work my way back to 200? If I have a double (234.004223), etc., I would like to round this to x significant digits in C#.  So far I can only find ways to round to x decimal places, but this simply removes the precision if there are any 0s in the number.  For example, 0.086 to one decimal place becomes 0.1, but I would like it to stay at 0.08. Should I vary input field lengths in a single page checkout form?