Tutorial by Examples: n

To get info from the requesting url (notice that req is the request object in the handler function of routes). Consider this route definition /settings/:user_id and this particular example /settings/32135?field=name // get the full path req.originalUrl // => /settings/32135?field=name // get...

NaN stands for "Not a Number." When a mathematical function or operation in JavaScript cannot return a specific number, it returns the value NaN instead. It is a property of the global object, and a reference to Number.NaN window.hasOwnProperty('NaN'); // true NaN; // NaN Perhaps con...

Unlike the WHERE clause, HAVING can be used with aggregate functions. An aggregate function is a function where the values of multiple rows are grouped together as input on certain criteria to form a single value of more significant meaning or measurement (Wikipedia). Common aggregate function...

The STUFF() function inserts a string into another string by first deleting a specified number of characters. The following example, deletes "Svr" and replaces it with "Server". This happens by specifying the start_position and length of the replacement. SELECT STUFF('SQL Svr D...

Linking to other Javadocs is done with the @link tag: /** * You can link to the javadoc of an already imported class using {@link ClassName}. * * You can also use the fully-qualified name, if the class is not already imported: * {@link some.other.ClassName} * * You can link to members...

Apple's Reachability class periodically checks the network status and alerts observers to changes. Reachability *internetReachability = [Reachability reachabilityForInternetConnection]; [internetReachability startNotifier];

Reachability uses NSNotification messages to alert observers when the network state has changed. Your class will need to become an observer. [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(reachabilityChanged:) name:kReachabilityChangedNotification object:nil]; Elsewher...

- (void)reachabilityChanged:(NSNotification *)note { Reachability* reachability = [note object]; NetworkStatus netStatus = [reachability currentReachabilityStatus]; if (netStatus == NotReachable) { NSLog(@"Network unavailable"); } }

- (void)reachabilityChanged:(NSNotification *)note { Reachability* reachability = [note object]; NetworkStatus netStatus = [reachability currentReachabilityStatus]; switch (netStatus) { case NotReachable: NSLog(@"Network unavailable"); br...

Many IDEs provide support for generating HTML from Javadocs automatically; some build tools (Maven and Gradle, for example) also have plugins that can handle the HTML creation. However, these tools are not required to generate the Javadoc HTML; this can be done using the command line javadoc tool. ...

Functional Interfaces Lambdas can only operate on a functional interface, which is an interface with just one abstract method. Functional interfaces can have any number of default or static methods. (For this reason, they are sometimes referred to as Single Abstract Method Interfaces, or SAM Interf...

This example demonstrates how Angular expressions are evaluated when using type="text" and type="number" for the input element. Consider the following controller and view: Controller var app = angular.module('app', []); app.controller('ctrl', function($scope) { $sco...

django-admin is a command line tool that ships with Django. It comes with several useful commands for getting started with and managing a Django project. The command is the same as ./manage.py , with the difference that you don't need to be in the project directory. The DJANGO_SETTINGS_MODULE envir...

You can create an HTML`...` template string tag function to automatically encodes interpolated values. (This requires that interpolated values are only used as text, and may not be safe if interpolated values are used in code such as scripts or styles.) class HTMLString extends String { static e...

// Java: List<String> list = people.stream().map(Person::getName).collect(Collectors.toList()); // Kotlin: val list = people.map { it.name } // toList() not needed

// Java: String joined = things.stream() .map(Object::toString) .collect(Collectors.joining(", ")); // Kotlin: val joined = things.joinToString() // ", " is used as separator, by default

// Java: Map<Department, List<Employee>> byDept = employees.stream() .collect(Collectors.groupingBy(Employee::getDepartment)); // Kotlin: val byDept = employees.groupBy { it.department }

// Java: Map<Department, Integer> totalByDept = employees.stream() .collect(Collectors.groupingBy(Employee::getDepartment, Collectors.summingInt(Employee::getSalary))); // Kotlin: val totalByDept = employees.groupBy { it.dept }.mapValues { it.v...

// Java: Map<Boolean, List<Student>> passingFailing = students.stream() .collect(Collectors.partitioningBy(s -> s.getGrade() >= PASS_THRESHOLD)); // Kotlin: val passingFailing = students.partition { it.grade >= PASS_THRESHOLD }

// Java: List<String> namesOfMaleMembersCollect = roster .stream() .filter(p -> p.getGender() == Person.Sex.MALE) .map(p -> p.getName()) .collect(Collectors.toList()); // Kotlin: val namesOfMaleMembers = roster.filter { it.gender == Person.Sex.MALE }.map { it.nam...