Tutorial by Examples: u

Insert a document called 'myFirstDocument' and set 2 properties, greetings and farewell 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('myCollect...

Find a document with the property { greetings: 'Hellu' } and change it to { greetings: 'Whut?' } const MongoClient = require('mongodb').MongoClient; const url = 'mongodb://localhost:27017/test'; MongoClient.connect(url, function (err, db) { if (err) throw new Error(err); db.collecti...

Delete a document with the property { greetings: 'Whut?' } 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').deleteOne(// Delete...

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...

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...

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...

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...

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...

Arrow functions may implicitly return values by simply omitting the curly braces that traditionally wrap a function's body if their body only contains a single expression. const foo = x => x + 1; foo(1); // -> 2 When using implicit returns, object literals must be wrapped in parenthesis s...

Arrow functions can behave very similar to classic functions in that you may explicitly return a value from them using the return keyword; simply wrap your function's body in curly braces, and return a value: const foo = x => { return x + 1; } foo(1); // -> 2

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...

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...

To initialize a static final fields that require using more than a single expression, a static initializer can be used to assign the value. The following example initializes a unmodifiable set of Strings: public class MyClass { public static final Set<String> WORDS; static {...

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...

It is possible to create a set of variables that can act similar to an array (although they are not an actual array object) by using spaces in the SET statement: @echo off SET var=A "foo bar" 123 for %%a in (%var%) do ( echo %%a ) echo Get the variable directly: %var% Result: ...