Tutorial by Examples: p

To check if a key exists in a Map, use the .has() method: map.has(key); Example: const map = new Map([[1, 2], [3, 4]]); console.log(map.has(1)); // true console.log(map.has(2)); // false

Map has three methods which returns iterators: .keys(), .values() and .entries(). .entries() is the default Map iterator, and contains [key, value] pairs. const map = new Map([[1, 2], [3, 4]]); for (const [key, value] of map) { console.log(`key: ${key}, value: ${value}`); // logs: // ke...

To get the numbers of elements of a Map, use the .size property: const map = new Map([[1, 2], [3, 4]]); console.log(map.size); // 2

To enable code shrinking with ProGuard, add minifyEnabled true to the appropriate build type in your build.gradle file. android { buildTypes { release { minifyEnabled true proguardFiles getDefaultProguardFile(‘proguard-android.txt'), 'pro...

Setting the state of an object graph (a collection of related entities) to Added is different than setting a single entity as Added (see this example). In the example, we store planets and their moons: Class model public class Planet { public Planet() { Moons = new HashSet<...

Building project dependencies can sometimes be a tedious task. Instead of publishing a package version to NPM and installing the dependency to test the changes, use npm link. npm link creates a symlink so the latest code can be tested in a local environment. This makes testing global tools and proje...

R provides two additional looping constructs, while and repeat, which are typically used in situations where the number of iterations required is indeterminate. The while loop The general form of a while loop is as follows, while (condition) { ## do something ## in loop body } whe...

Iterating over connected serial ports using System.IO.Ports; string[] ports = SerialPort.GetPortNames(); for (int i = 0; i < ports.Length; i++) { Console.WriteLine(ports[i]); } Instantiating a System.IO.SerialPort object using System.IO.Ports; SerialPort port = new SerialPort(); ...

This example is about replacing a List element while ensuring that the replacement element is at the same position as the element that is replaced. This can be done using these methods: set(int index, T type) int indexOf(T type) Consider an ArrayList containing the elements "Program sta...

A conversion that involves calling an explicit constructor or conversion function can't be done implicitly. We can request that the conversion be done explicitly using static_cast. The meaning is the same as that of a direct initialization, except that the result is a temporary. class C { std:...

static_cast can perform any implicit conversion. This use of static_cast can occasionally be useful, such as in the following examples: When passing arguments to an ellipsis, the "expected" argument type is not statically known, so no implicit conversion will occur. const double x = ...

For a class Person like: public class Person { public string Name { get; set; } public int Age { get; set; } public string Clothes { get; set; } } var person1 = new Person { Name = "Jon", Age = 20, Clothes = "some clothes" }; var person2 = new Person { Name ...

For given type Person: public class Person { public string Name { get; set; } public int Age { get; set; } public string Clothes { get; set; } } List<Person> persons = new List<Person> { new Person{ Name = "Jon", Age = 20, Clothes = "some clothes...

float [(n)] real These data types are used to store floating point numbers. Since these types are intended to hold approximate numeric values only, these should not be used in cases where any rounding error is unacceptable. However, if you need to handle very large numbers, or numbers with an ...

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All modern JavaScript JIT compilers trying to optimize code based on expected object structures. Some tip from mdn. Fortunately, the objects and properties are often "predictable", and in such cases their underlying structure can also be predictable. JITs can rely on this to make pred...

You can use built-in functions to run PHP processes as forks. This is the most simple way to achieve parallel work if you don't need your threads to talk to each other. This allows you to put time intensive tasks (like uploading a file to another server or sending an email) to another thread so you...

1 Tag Name Represents a tag name available in the DOM. For example $('p') selects all paragraphs <p> in the document. 2 Tag ID Represents a tag available with the given ID in the DOM. For example $('#some-id') selects the single element in the document that has an ID of some-id. 3 ...

1. A Simple Complete Example We could use this sample code to upload the files selected by the user every time a new file selection is made. <input type="file" id="file-input" multiple>   var files; var fdata = new FormData(); $("#file-input").on("cha...

One of the most common operations in erlang is pattern matching. It is used when assigning a value to a variable, in function declarations and in control-flow structures like case and receive statements. A pattern matching operation needs at least 2 parts: a pattern, and a term against wich the patt...