why does browser throw Error for var null; ?  I am reading  and I know undefined is a global variable different from null.    But I am just curious about that why it throws Error when dovar null; in contrast, when var Number=123,var Boolean=123,var Object=123,var undefined=123(although useless), etc.,it's ok.  As far as I know, null is not a reserved word and keyword in JavaScript. It should be a primitive type.  How does var work exactly in relation to null?
What JavaScript keywords (function names, variables, etc) are reserved?
I'd like to have Ubuntu installed on a USB stick, that I could plug in (almost) any computer and boot from it, and that I could use (almost) normally, as if it was installed on that computer. I'd also like to have a data partition on it that could be used by (almost) any computer, mostly to store some portable apps, just in case.    I've been told that if I installed Ubuntu in BIOS mode, I wouldn't be able to boot from a computer in UEFI mode, and vice versa.  Since I'd like to be able to boot on any computer, it's a big problem.  What can I do to be able to boot on computers in BIOS or UEFI modes in my case?  I've been searching for solutions but most of them are for specific needs that are different than mine, so it's difficult to extract the minimum requirements from those solutions to apply them to my problem.  Is there a simple, "clean" and quite generic solution to this problem?  I'd appreciate some explainations about the reasons why a specific solution is good or a specific step is needed.    My current setup:   USB stick:  OS: Xubuntu 16.04 i386 installation: full install (from a Live USB built with Rufus) drivers: none proprietary file systems:    partition table:    2: , /boot/efi, 128 Mio, FAT32, [boot,esp] 3: , 128 Mio, HFS+ 4: , 2 Mio, [bios_grub] 5: swap, 512 Mio 6: , /, 24 Gio, ext4, defaults,errors=remount-ro,lazytime,commit=60 1: , /media/data, ~3.6 Gio, FAT32, defaults,lazytime,check=strict  RAM:   /tmp, tmpfs, defaults,nosuid,nodev,noexec,mode=1777   swap:    vm.swappiness=5 swap partition: 512 Mio, for emergency zRAM swap files:    /var/swap/hib.swp: same size as RAM, for hibernation, generated by a script at startup /var/swap/opt.swp: if needed, generated by a script   overprovisioning: ~5.6%   built-in: ~1.2 Gio (apparently) added: 512 Mio  scheduler: deadline Let $\Gamma$ denote the positively oriented circle of radius $2$ with center at the origin. Let $f$ be an analytic function on $\{z \in\mathbb{C} : |z|&gt;1 \}$, and let $$\lim_{z\to \infty}f(z)=0.$$  Prove that $$ f(z)=\frac{1}{2\pi i} \int_{\Gamma} \frac{f(\xi)}{z-\xi}d\xi,  $$ for all $z\in\mathbb{C}$ with $|z|&gt;2$.  I have no idea how to even start. Any hint will be appreciated. In Helgason, "Differential Geometry, Lie Groups and Symmetric Spaces"  we have the formula for the exterior derivative  $(p+1)d\omega(X_{1}, \ldots X_{p+1})=\Sigma_{i=1}^{p+1} (-1)^{i+1} X_{i} \cdot \omega(X_{1}, \ldots , \hat{X_{i}}, \ldots X_{p+1})+\Sigma_{i&lt;j} (-1)^{i+j}\omega([X_{i}, X_{j}], X_{1}, \ldots , \hat{X_{i}}, \ldots \hat{X_{j}}, \ldots , X_{p+1})$  but in other sources on-line they have the same formula without the factor of $p+1$ on the left-hand side.  Are there two different definitions of the exterior derivative, or is there an error in Helgason? Disk full, du tells different. How to further investigate? I have a SCSI disk in a server (hardware Raid 1), 32G, ext3 filesytem. df tells me that the disk is 100% full. If I delete 1G this is correctly shown.  However, if I run a du -h -x / then du tells me that only 12G are used (I use -x because of some Samba mounts).  So my question is not about subtle differences between the du and df commands but about how I can find out what causes this huge difference?  I rebooted the machine for a fsck that went w/out errors. Should I run badblocks? lsof shows me no open deleted files, lost+found is empty and there is no obvious warn/err/fail statement in the messages file.  Feel free to ask for further details of the setup. Bash auto_completion with Xubuntu and xrdp from windows I'm using Xubuntu and connecting over RemoteDesktop with Windows 7.  Everything works fine, but the auto_completion in my bash doesn't work. I checked the .bashrc file in my home directory and also the /etc/bash.bashrc.  I uncommend the lines below in my local bashrc configuration and also in bash.bashrc, but nothing changes.  if ! shopt -oq posix; then   if [ -f /usr/share/bash-completion/bash_completion ]; then     . /usr/share/bash-completion/bash_completion   elif [ -f /etc/bash_completion ]; then     . /etc/bash_completion   fi fi Show timestamp of a vote in the tooltip when mousing over it Sometimes I come across an old question or answer that I voted on in the past, but I don't clearly remember when (or sometimes even why) I voted it up or down. Being able to see the date/time that I cast a vote would help me remember my mindset at the time.   When mousing over the toggled vote, the tooltip reads the same as if I hadn't voted, with no further information. For example:     This answer is useful (click again to undo)   The only way to get the timestamp is if I try to click the vote to undo it and get the locked vote message:     You last voted on this answer [datetime] Your vote is now locked in unless this answer is edited   However this requires me to guess that the vote is locked - if there was an edit since then I'll actually undo the vote and erase the info I was looking for.  Feature request: Please add the vote timestamp to the tooltip when mousing over a cast vote. This is already done with the green acceptance checkmark for example. Is there a quick way to reset a .blend files windows and settings to default Whenever I download a .blend from someone all of the windows and settings are the way they have left them as it is saved in the file. It takes way to long to rearrange every window and toolbar to the way it is by default. Is there any tool or shortcut that can reset the UI to blenders default and just leave the actual contents of the file? The only way I could do this is by creating a new file and using link/append but this is not the best option. Tokenizing strings in C I have been trying to tokenize a string using SPACE as delimiter but it doesn't work. Does any one have suggestion on why it doesn't work?  Edit: tokenizing using:  strtok(string, " ");   The code is like the following  pch = strtok (str," "); while (pch != NULL) {   printf ("%s\n",pch);   pch = strtok (NULL, " "); } Why is it so difficult to pull an immersed mug out of the water? Suppose I put a mug in the water and then tilt it so that the water gets inside. It then floats due to buoyant force. But if I try to pull it out then a lot of force is needed. That's due to suction? What exactly happens at the moment when the force I apply is enough to pull the mug out? And what causes the loud pop sound when that happens? Why do we have wrinkly fingers after swimming? I found an explanation for my question here , which suggests that water washes out sebum (special oil, which covers our skin) and water gets into outer layer of now unprotected skin by osmosis. This article also suggests that fingers are not really shriveled - they are water-logged. But is this right? I think I observed many times my wrinkly fingers after swimming, but I never felt that they are water-logged. Any thought on this matter would be highly appreciated. Why doesn't Steam start? When I try to start Steam nothing happens. Reinstall doesn't help.  $ steam Running Steam on ubuntu 13.04 64-bit STEAM_RUNTIME is enabled automatically Installing breakpad exception handler for appid(steam)/version(1378500910_client) Installing breakpad exception handler for appid(steam)/version(1378500910_client) Installing breakpad exception handler for appid(steam)/version(1378500910_client) unlinked 0 orphaned pipes removing stale semaphore last operated on by process 7278 with name 0eBlobRegistryMutex_DC7EBB4AEA41D3C6C74E5EFFD6757CEC removing stale semaphore last operated on by process 7278 with name 0eBlobRegistrySignal_DC7EBB4AEA41D3C6C74E5EFFD6757CEC removing stale semaphore last operated on by process 7278 with name 0emSteamEngineInstance removing stale semaphore last operated on by process 7278 with name 0eSteamEngineLock Gtk-Message: Failed to load module "overlay-scrollbar" Installing breakpad exception handler for appid(steam)/version(1378500910_client) [0913/182910:WARNING:proxy_service.cc(958)] PAC support disabled because there is no system implementation   How to fix it? macOS Catalina: "App is damaged and can't be opened. You should move it to the trash." Experiencing a problem with several apps after installing macOS Catalina.  When the app is downloaded from the internet I get the error:     "APP NAME" is damaged and can't be opened. You should move it to the trash.   Any workarounds to bypass macOS gatekeeper for specific apps? How to control a motor with only relays and push button? Hello I´ve been working in this project for some days, I need to make a circuit with only relays that can make a dc motor start, stop and a reverse. The thing is that when you push the start or the reverse button the motor need to keep running, I can´t keep it pushed.  This is as far as I can get. SW1 turns the engine on, SW5 turns it off and SW7 reverse the motor but only if it is already running. What i need is that the reverse button also turns the engine on. Please help.  notes: -i can only use three push buttons and as many relays as needed. Yes is a school assignment.  THANKS! The repository 'http://ppa.launchpad.net/mdeguzis/libregeek/ubuntu focal Release' does not have a Release file How to reliably keep an SSH tunnel open? I use an SSH tunnel from work to go around various idotic firewalls (it's ok with my boss :)). The problem is, after a while the ssh connection usually hangs, and the tunnel is broken.  If I could at least monitor the tunnel automatically, I could restart the tunnel when it hangs, but I haven't even figured a way of doing that.  Bonus points for the one who can tell me how to prevent my ssh connection from hanging, of course! How does extra damage work for critical hits? I'm a bit confused on how extra damage works for critical hits. Let's take the following example: A thief with sneak attack rolls a crit. I'm under the impression he rolls double his normal attack damage dice AND double his Sneak Attack damage dice. Is this accurate? Another example, I finished DM-ing my first campaign recently. The Giant Spider enemy monster has an melee attack that causes a constitution saving throw. If the player fails, the enemy rolls an additional 2D8 of damage. In this situation, if there was a critical hit, and the player failed their saving throw, would I also roll double dice on the additional damage? Or is that considered a separate attack? Suppose, I want to refer multiple equations (1), (2), (3), (4), (5) and (7) so that they appear as (1-5, 7):  \documentclass[fleqn,preprint,10pt]{article} \usepackage{amsmath} \usepackage{amssymb} \usepackage{amsfonts} \begin{document} \begin{align} \label{1}\psi([e_1,e_2]) = \psi(e_2) = e_2 = (e_2,2e_3) = (-2e_3,e_2) = (\psi(e_1), \psi(e_2))\\ \label{2}\psi([e_1,e_3]) = \psi(2e_3) = 2e_1 = (e_1,2e_3) = (-2e_3,e_1) = (\psi(e_1),\psi(e_3))\\ \label{3}\psi([e_2,e_3]) = 0 = (e_2,e_1) = (\psi(e_2),\psi(e_3)),\\ \label{4}\left\{e_4, e_1\right\},\,\,\,\left\{e_4, e_2\right\},\,\,\,\left\{e_4, e_3\right\},\,\,\,\left\{e_4, e_1+\epsilon\,e_2\right\},\\ \label{5}\left\{e_1, e_2\right\},\,\,\,\left\{e_3, e_1\right\},\,\,\,\left\{e_3, e_2\right\},\\ \label{6}\left\{e_4, e_1\right\},\,\,\,\left\{e_4, e_2\right\},\,\,\,\left\{e_4, e_3\right\},\,\,\,\left\{e_4, e_1+\epsilon\,e_2\right\},\\ \label{7}\text{Nor}_{L_4\oplus L_3}\left(\{e_2\}\right)/\{e_2\}=\,\{e_1, e_3, e_4\} \end{align} \end{document} Idiom or expression that would imply "someone is a habitual liar" I'm looking for an idiom or expression for describing people who tell lies out of habit (so you cannot trust them at all).   I know that these people are called , but I'm not looking for psychological terms.  Is there any idiom or expression for describing such people?   For example:     "Did X tell that to you?! Come on, don't believe him/her. Don't you know he/she ___ (=is a habitual liar)?" Settings API enable default settings on theme install? I am still learning settings API so please forgive my noob question. I have three fields: a checkbox, colorpicker and text field (they are working), but I would like to do this: when the theme is installed add "checked" state to my checkbox but allow user to "unchecked" it ,and if empty add default color to my colorpicker... I have no idea how to do this so please help me!  My code looks like this now (thanks to @Chip Bennett! ) :  &lt;?php add_action('admin_menu','create_theme_options_page'); function create_theme_options_page(){ add_options_page('Theme Options','Theme Options','administrator',__FILE__,'build_options_page'); }    function build_options_page(){    ?&gt;    &lt;div id="theme-options-wrap"&gt;    &lt;div style="float:left;margin-top:19px;position:absolute;" class="icon32" id="icon-tools"&gt;&lt;br/&gt;&lt;/div&gt;    &lt;h2&gt;My options page&lt;/h2&gt;    &lt;form method="post" action="options.php"&gt;    &lt;?php settings_fields('plugin_options');?&gt;    &lt;?php do_settings_sections(__FILE__); ?&gt;    &lt;p class="submit"&gt;    &lt;input name="Submit" type="submit" class="button-primary" value="&lt;?php esc_attr_e('Save changes');?&gt;"/&gt;    &lt;/p&gt;    &lt;/form&gt;    &lt;/div&gt;    &lt;?php    }       add_action('admin_init','register_and_build_fields');      function register_and_build_fields(){      register_setting('plugin_options','plugin_options','validate_setting');      add_settings_section('main_section','&lt;br/&gt;&lt;br/&gt;Main Settings','section_cb',__FILE__);      add_settings_field('banner_heading','Banner Heading:','banner_heading_setting',__FILE__,'main_section');      add_settings_field('display_sidebar','Display Sidebar:','display_sidebar_setting',__FILE__,'main_section');      add_settings_field('display_colorpicker','Display Colorpicker:','display_colorpicker_setting',__FILE__,'main_section');      }        //Install Iris colorpicker        add_action( 'admin_enqueue_scripts', 'mw_enqueue_color_picker' );        function mw_enqueue_color_picker( $hook_suffix ) {        // first check that $hook_suffix is appropriate for your admin page        wp_enqueue_style( 'wp-color-picker' );        wp_enqueue_script( 'my-script-handle', get_template_directory_uri() . '/js/my-script.js', array( 'wp-color-picker' ), false, true );        }           //Colorpicker          //Now how to add a default color on theme install?          function display_colorpicker_setting(){          $options = get_option('plugin_options');          echo"&lt;input type='text' id='color1' name='plugin_options[display_colorpicker]' value='{$options['display_colorpicker']}'/&gt;";          }            //Sidebar checkbox           //Now how to add a default state "checked" on theme install?           function display_sidebar_setting(){           $options = get_option('plugin_options');           echo "&lt;input type='checkbox' name='plugin_options[display_sidebar]' {$options['display_sidebar']} id='display_sidebar' /&gt;";           }              //Banner Heading             function banner_heading_setting(){             $options = get_option('plugin_options');             echo "&lt;input name='plugin_options[banner_heading]' type='text' value='{$options['banner_heading']}'/&gt;";             }               //Validate our settings here               function validate_setting($plugin_options){                  return $plugin_options;               }                 function section_cb(){                } ?&gt; CAST and IsNumeric Why would the following query return "Error converting data type varchar to bigint"?  Doesn't IsNumeric make the CAST safe?  I've tried every numeric datatype in the cast and get the same "Error converting..." error.  I don't believe the size of the resulting number is a problem because overflow is a different error.  The interesting thing is, in management studio, the results actually show up in the results pane for a split second before the error comes back.  SELECT CAST(myVarcharColumn AS bigint)   FROM myTable   WHERE IsNumeric(myVarcharColumn) = 1 AND myVarcharColumn IS NOT NULL   GROUP BY myVarcharColumn   Any thoughts?