Tutorial by Examples: o

Delete ALL documents with a 'farewell' property set to 'okay'. const MongoClient = require('mongodb').MongoClient; const url = 'mongodb://localhost:27017/test'; MongoClient.connect(url, function (err, db) { if (err) throw new Error(err); db.collection('myCollection').deleteMany(// M...

.find() method allows us to search through the descendants of these elements in the DOM tree and construct a new jQuery object from the matching elements. HTML <div class="parent"> <div class="children" name="first"> <ul> ...

You can use the plus (+) operator to concatenate strings: 'Dart ' + 'is ' + 'fun!'; // 'Dart is fun!' You can also use adjacent string literals for concatenation: 'Dart ' 'is ' 'fun!'; // 'Dart is fun!' You can use ${} to interpolate the value of Dart expressions within strings. The curly...

Programmatically generating a String is best accomplished with a StringBuffer. A StringBuffer doesn't generate a new String object until toString() is called. var sb = new StringBuffer(); sb.write("Use a StringBuffer"); sb.writeAll(["for ", "efficient ", "stri...

for arg; do echo arg=$arg done A for loop without a list of words parameter will iterate over the positional parameters instead. In other words, the above example is equivalent to this code: for arg in "$@"; do echo arg=$arg done In other words, if you catch yourself wri...

# The following shell function will be used to generate completions for # the "nuance_tune" command. _nuance_tune_opts () { local curr_arg prev_arg curr_arg=${COMP_WORDS[COMP_CWORD]} prev_arg=${COMP_WORDS[COMP_CWORD-1]} # The "config" option takes a file arg, so ...

template <class InputIterator, class T> typename iterator_traits<InputIterator>::difference_type count (InputIterator first, InputIterator last, const T& val); Effects Counts the number of elements that are equal to val Parameters first => iterator pointing to the beginnin...

template <class InputIterator, class UnaryPredicate> typename iterator_traits<InputIterator>::difference_type count_if (InputIterator first, InputIterator last, UnaryPredicate red); Effects Counts the number of elements in a range for which a specified predicate function is true P...

If we want to order the data differently for per group, we can add a CASE syntax to the ORDER BY. In this example, we want to order employees from Department 1 by last name and employees from Department 2 by salary. IdFNameLNamePhoneNumberManagerIdDepartmentIdSalaryHireDate1JamesSmith1234567890NUL...

We are so used to the name D3.js that it's possible to forget that D3 is actually DDD (Data-Driven Documents). And that's what D3 does well, a data-driven approach to DOM (Document Object Model) manipulation: D3 binds data to DOM elements and manipulates those elements based on the bounded data. Le...

git log --pretty=format:"%Cgreen%ci %Cblue%cn %Cgreen%cr%Creset %s" This will give a nice overview of all commits (1 per line) with date, user and commit message. The --pretty option has many placeholders, each starting with %. All options can be found here

It is not possible to add and commit an empty folder in Git due to the fact that Git manages files and attaches their directory to them, which slims down commits and improves speed. To get around this, there are two methods: Method one: .gitkeep One hack to get around this is to use a .gitkeep fil...

Arrow functions are lexically scoped; this means that their this Binding is bound to the context of the surrounding scope. That is to say, whatever this refers to can be preserved by using an arrow function. Take a look at the following example. The class Cow has a method that allows for it to pr...

Arrow functions do not expose an arguments object; therefore, arguments would simply refer to a variable in the current scope. const arguments = [true]; const foo = x => console.log(arguments[0]); foo(false); // -> true Due to this, arrow functions are also not aware of their caller/ca...

xcrun uses the system default Xcode version (set via xcode-select) to locate and execute command line tools from the Xcode application bundle, e.g., llvm-cov. # Generate code coverage reports via llvm-cov # /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin xc...

C extensions are comprised of two general pieces: The C Code itself. The extension configuration file. To get started with your first extension put the following in a file named extconf.rb: require 'mkmf' create_makefile('hello_c') A couple of things to point out: First, the name hell...

Use Spliterators.spliterator() or Spliterators.spliteratorUnknownSize() to convert an iterator to a stream: Iterator<String> iterator = Arrays.asList("A", "B", "C").iterator(); Spliterator<String> spliterator = Spliterators.spliteratorUnknownSize(itera...

In this example we have only one object but it is shared between/executed on different threads. Ordinary usage of fields to save state would not be possible because the other thread would see that too (or probably not see). public class Test { public static void main(String[] args) { ...

Reduction is the process of applying a binary operator to every element of a stream to result in one value. The sum() method of an IntStream is an example of a reduction; it applies addition to every term of the Stream, resulting in one final value: This is equivalent to (((1+2)+3)+4) The reduc...

Sun / Oracle releases of Java SE come in two forms: JRE and JDK. In simple terms, JREs support running Java applications, and JDKs also support Java development. Java Runtime Environment Java Runtime Environment or JRE distributions consist of the set of libraries and tools needed to run and mana...