Tutorial by Examples: d

After installation process, the following lines should be entered in mongo shell (client terminal). > db.world.insert({ "speech" : "Hello World!" }); > cur = db.world.find();x=cur.next();print(x["speech"]); Hello World! Explanation: In the first line,...

WiredTiger supports LSM trees to store indexes. LSM trees are faster for write operations when you need to write huge workloads of random inserts. In WiredTiger, there is no in-place updates. If you need to update an element of a document, a new document will be inserted while the old document will...

This uses the Dropbox .NET SDK to download a file from the Dropbox API at the remote path to the local file "Test", while tracking progress: var response = await client.Files.DownloadAsync(path); ulong fileSize = response.Response.Size; const int bufferSize = 1024 * 1024; var buffer ...

We use Notification.requestPermission to ask the user if he/she wants to receive notifications from our website. Notification.requestPermission(function() { if (Notification.permission === 'granted') { // user approved. // use of new Notification(...) syntax will now be succe...

It's an emulation of classical inheritance using prototypical inheritance which shows how powerful prototypes are. It was made to make the language more attractive to programmers coming from other languages. 6 IMPORTANT NOTE: Since ES6 it doesn't make sense to use pseudo-calssical inheritance sinc...

After the user has approved a request for permission to send notifications, we can send a simple notification that says Hello to the user: new Notification('Hello', { body: 'Hello, world!', icon: 'url to an .ico image' }); This will send a notification like this: Hello Hello, world!

5 It allows us to define a property in an existing object using a property descriptor. var obj = { }; Object.defineProperty(obj, 'foo', { value: 'foo' }); console.log(obj.foo); Console output foo Object.defineProperty can be called with the following options: Object.definePropert...

5 Using property descriptors we can make a property read only, and any attempt to change it's value will fail silently, the value will not be changed and no error will be thrown. The writable property in a property descriptor indicates whether that property can be changed or not. var a = { }; ...

5 A property's descriptor can be locked so no changes can be made to it. It will still be possible to use the property normally, assigning and retrieving the value from it, but any attempt to redefine it will throw an exception. The configurable property of the property descriptor is used to dis...

5 Treat a property as a combination of two functions, one to get the value from it, and another one to set the value in it. The get property of the property descriptor is a function that will be called to retrieve the value from the property. The set property is also a function, it will be call...

Syntax: SELECT * FROM table_name Using the asterisk operator * serves as a shortcut for selecting all the columns in the table. All rows will also be selected because this SELECT statement does not have a WHERE clause, to specify any filtering criteria. This would also work the same way if you...

This query will return the number of tables in the specified database. USE YourDatabaseName SELECT COUNT(*) from INFORMATION_SCHEMA.TABLES WHERE TABLE_TYPE = 'BASE TABLE' Following is another way this can be done for all user tables with SQL Server 2008+. The reference is here. SELECT COUNT(...

The following queries will return a list of all Stored Procedures in the database, with basic information about each Stored Procedure: SQL Server 2005 SELECT * FROM INFORMATION_SCHEMA.ROUTINES WHERE ROUTINE_TYPE = 'PROCEDURE' The ROUTINE_NAME, ROUTINE_SCHEMA and ROUTINE_DEFINITION columns are...

While object property notation is usually written as myObject.property, this will only allow characters that are normally found in JavaScript variable names, which is mainly letters, numbers and underscore (_). If you need special characters, such as space, ☺, or user-provided content, this is poss...

Sometimes the property name needs to be stored into a variable. In this example, we ask the user what word needs to be looked up, and then provide the result from an object I've named dictionary. var dictionary = { lettuce: 'a veggie', banana: 'a fruit', tomato: 'it depends on who yo...

To find a character or another string, you can use std::string::find. It returns the position of the first character of the first match. If no matches were found, the function returns std::string::npos std::string str = "Curiosity killed the cat"; auto it = str.find("cat"); ...

The function std::find, defined in the <algorithm> header, can be used to find an element in a std::vector. std::find uses the operator== to compare elements for equality. It returns an iterator to the first element in the range that compares equal to the value. If the element in question is...

An array can easily be converted into a std::vector by using std::begin and std::end: C++11 int values[5] = { 1, 2, 3, 4, 5 }; // source array std::vector<int> v(std::begin(values), std::end(values)); // copy array to new vector for(auto &x: v) std::cout << x << &q...

When you start a thread, it will execute until it is finished. Often, at some point, you need to (possibly - the thread may already be done) wait for the thread to finish, because you want to use the result for example. int n; std::thread thread{ calculateSomething, std::ref(n) }; //Doing some...

You cannot pass a reference (or const reference) directly to a thread because std::thread will copy/move them. Instead, use std::reference_wrapper: void foo(int& b) { b = 10; } int a = 1; std::thread thread{ foo, std::ref(a) }; //'a' is now really passed as reference thread.join()...