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How can I determine if a variable is 'undefined' or 'null'?
...enceError and break execution if variable is not defined or referred to at all in the code, using typeof is safer.
– Mani Gandham
Jun 15 '14 at 9:49
59
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What does the [Flags] Enum Attribute mean in C#?
... Such collections are often used with bitwise operators, for example:
var allowedColors = MyColor.Red | MyColor.Green | MyColor.Blue;
Note that the [Flags] attribute doesn't enable this by itself - all it does is allow a nice representation by the .ToString() method:
enum Suits { Spades = 1, Clu...
jQuery Validate - Enable validation for hidden fields
...ry, this could break an existing
setup. In the unlikely case that it actually does, you can fix it by
setting the ignore-option to “[]” (square brackets without the
quotes)."
To change this setting for all forms:
$.validator.setDefaults({
ignore: [],
// any other default option...
How to copy a selection to the OS X clipboard
...xists only for X11 (unless you build vim with +X11 support, which will install a X11 server XQuartz in OS X), while OS X doesn't use X11 as its windows system.
– nn0p
Nov 27 '16 at 18:20
...
How do I completely uninstall Node.js, and reinstall from beginning (Mac OS X)
My version of node is always v0.6.1-pre even after I install brew node and NVM install v0.6.19.
28 Answers
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Summarizing multiple columns with dplyr? [duplicate]
...
The dplyr package contains summarise_all for this aim:
library(dplyr)
df %>% group_by(grp) %>% summarise_all(list(mean))
#> # A tibble: 3 x 5
#> grp a b c d
#> <int> <dbl> <dbl> <dbl> <dbl>
#>...
Get specific object by id from array of objects in AngularJS
...by id, the result is an array
// so we select the element 0
single_object = $filter('filter')(foo.results, function (d) {return d.id === 2;})[0];
// If you want to see the result, just check the log
console.log(single_object);
}]);
Plunker: http://plnkr.co/edit/5E7FYqNNqDuqFBlyDq...
How to implement has_many :through relationships with Mongoid and mongodb?
...uire multiple queries.
https://github.com/mongoid/mongoid/issues/544
Normally if you have a many-many relationship in a RDBMS you would model that differently in MongoDB using a field containing an array of 'foreign' keys on either side. For example:
class Physician
include Mongoid::Document
...
android asynctask sending callbacks to ui [duplicate]
...tivity I'm initializing the asynctask, and I want the asynctask to report callbacks back to my activity.
Is it possible? Or does the asynctask must be in the same class file as the activity?
...
SQL Server 2008 can't login with newly created user
...
SQL Server was not configured to allow mixed authentication.
Here are steps to fix:
Right-click on SQL Server instance at root of Object Explorer, click on Properties
Select Security from the left pane.
Select the SQL Server and Windows Authentication m...