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In MongoDB aggregate(), use $group and aggregate collection. Let us create a collection with documents −> db.demo616.insertOne({"details":{"Name":"Chris", "Age":21}}); { "acknowledged" : true, "insertedId" : ObjectId("5e99bfac65492f6c60d00283") } > db.demo616.insertOne({"details":{"Name":"Chris", "Age":22}}); { "acknowledged" : true, "insertedId" : ObjectId("5e99bfb065492f6c60d00284") } > db.demo616.insertOne({"details":{"Name":"Bob", "Age":23}}); { "acknowledged" : true, "insertedId" : ObjectId("5e99bfb865492f6c60d00285") } > db.demo616.insertOne({"details":{"Name":"Sam", "Age":21}}); { "acknowledged" : true, "insertedId" : ObjectId("5e99bfbd65492f6c60d00286") } > db.demo616.insertOne({"details":{"Name":"Chris", "Age":24}}); { "acknowledged" : true, "insertedId" : ObjectId("5e99bfc165492f6c60d00287") }Display all documents from a collection with the help of find() method −> db.demo616.find();This will produce the following output −{ "_id" ... Read More
The $type selects documents where the value of the field is an instance of the specified BSON type. Let us create a collection with documents −> db.demo615.insert({"Value":100}); WriteResult({ "nInserted" : 1 }) > db.demo615.insert({"Value":"100"}); WriteResult({ "nInserted" : 1 }) > db.demo615.insert({"Value":"300"}); WriteResult({ "nInserted" : 1 }) > db.demo615.insert({"Value":300}); WriteResult({ "nInserted" : 1 })Display all documents from a collection with the help of find() method −> db.demo615.find();This will produce the following output −{ "_id" : ObjectId("5e99bb3465492f6c60d0027f"), "Value" : 100 } { "_id" : ObjectId("5e99bb3865492f6c60d00280"), "Value" : "100" } { "_id" : ObjectId("5e99bb3c65492f6c60d00281"), "Value" : "300" } { "_id" : ObjectId("5e99bb4265492f6c60d00282"), "Value" ... Read More
The ({$natural − 1}) works like LIFO(LAST IN FIRST OUT), that means last inserted document will be shown first.Let us create a collection with documents −> db.demo614.insertOne({"CountryName":"US"}); { "acknowledged" : true, "insertedId" : ObjectId("5e988cddf6b89257f5584d8e") } > db.demo614.insertOne({"CountryName":"UK"}); { "acknowledged" : true, "insertedId" : ObjectId("5e988ce0f6b89257f5584d8f") } > db.demo614.insertOne({"CountryName":"AUS"}); { "acknowledged" : true, "insertedId" : ObjectId("5e988ce3f6b89257f5584d90") } > db.demo614.insertOne({"CountryName":"IND"}); { "acknowledged" : true, "insertedId" : ObjectId("5e988cebf6b89257f5584d91") }Display all documents from a collection with the help of find() method −> db.demo614.find();This will produce the following output −{ "_id" : ObjectId("5e988cddf6b89257f5584d8e"), "CountryName" : "US" } { ... Read More
To import and export modules using JavaScript, the code is as follows −Note − To run this example you will need to run a localhost server.INDEX.htmlExample Live Demo Document body { font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif; } .result { font-size: 18px; font-weight: 500; } JavaScript Importing and Exporting Modules IMPORT Click on the above button to import module script.jsimport test from './sample.js'; document.querySelector('.Btn').addEventListener('click',()=>{ test(); })sample.jslet resultEle = document.querySelector(".result"); export default function testImport(){ resultEle.innerHTML = 'Module testImport has been imported'; }OutputOn clicking the ‘IMPORT’ button −
To generate random hex codes of color using JavaScript, the code is as follows −Example Live Demo Document body { font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif; } .result { box-sizing: border-box; font-size: 18px; font-weight: 500; color: white; width: 150px; height: 150px; text-align: center; padding-top: 4%; } Generate random hex codes of color GENERATE Click on the above button to generate a random hex color code let resultEle = document.querySelector(".result"); let hexCode = "0123456789ABCDEF"; let Color = "#"; document.querySelector(".Btn").addEventListener("click", () => { for (let i = 0; i < 6; i++) Color += hexCode[Math.floor(Math.random() * 16)]; resultEle.style.backgroundColor = Color; resultEle.innerHTML = Color; }); OutputOn clicking the ‘GENERATE’ button −
The JavaScript File WebAPI file.name property returns only the name of the file without the path.Following is the code for the File WebApi File.name property −Example Live Demo Document body { font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif; } .result { font-size: 18px; font-weight: 500; color: red; } JavaScript file.name property Upload a file using the above input type to get its file name let resultEle = document.querySelector(".result"); document .querySelector(".fileInput") .addEventListener("change", (event) => { resultEle.innerHTML += "File name = " + event.target.files[0].name; }); OutputOn clicking the ‘Choose file’ button and selecting a file −
The JavaScript unescape() function is used to decode an encoded string. It is deprecated in JavaScript version 1.5.Following is the code for the unescape() function −Example Live Demo Document body { font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif; } .sample, .result { font-size: 18px; font-weight: 500; color: red; } .result { color: blueviolet; } JavaScript unescape() property CLICK HERE CLICK the above button to decode the above url ... Read More
The JavaScript undefined property specifies if a variable has been declared or assigned a value yet.Following is the code for the JavaScript undefined property −Example Live Demo Document body { font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif; } .sample { font-size: 18px; font-weight: 500; color: red; } JavaScript undefined property CLICK HERE CLICK the above button to know if variable age has been defined or not let sampleEle = document.querySelector(".sample"); let ... Read More
Promises in JavaScript allow us to do asynchronous operations where the value is not known in advanced when the promise was being created. A promise can have three states pending, fulfilled and rejected.Following is the code for promises in JavaScript −Example Live Demo Document body { font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif; } .sample { font-size: 18px; font-weight: 500; color: red; } JavaScript Promises CLICK HERE Click on the above button to display username ... Read More
Following is an example for numbers in JavaScript −Example Live Demo Document body { font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif; } .sample{ font-size: 18px; font-weight: 500; color: red; } JavaScript Numbers CLICK HERE Click on the above button to see numbers in JavaScript let sampleEle = document.querySelector(".sample"); let a =22; let b = 1.523; let c = 99; document.querySelector(".Btn").addEventListener("click", () => { sampleEle.innerHTML = 'a = ' + a + ''; sampleEle.innerHTML += 'b =' + b + ''; sampleEle.innerHTML += 'c = ' + c + ''; sampleEle.innerHTML += 'a + c = ' + (a+c) + ''; }); OutputOn clicking the ‘CLICK HERE’ button −