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Javascript Articles
Page 521 of 534
What is ECMAScript and how it is related to JavaScript?
JavaScript conforms to ECMAScript standard. JavaScript was first known as LiveScript, but Netscape changed its name to JavaScript, possibly because of the excitement being generated by Java. JavaScript made its first appearance in Netscape 2.0 in 1995 with the name LiveScript. The general-purpose core of the language embedded in Netscape, Internet Explorer, and other web browsers.The ECMAScript Edition 5 standard was the first update to be released in over four years. JavaScript 2.0 conforms to Edition 5 of the ECMAScript standard, and the difference between the two is extremely minor.The 8th edition, known as ECMAScript 2017, came in June 2017.The ...
Read MoreJasmine.js comparing arrays
Arrays can be compared in 2 ways −They refer to the same array object in memory.They may refer to different objects but their contents are all equal.For case 1, jasmine provides the toBe method. This checks for reference. For example, Exampledescribe("Array Equality", () => { it("should check for array reference equility", () => { let arr = [1, 2, 3]; let arr2 = arr // Runs successfully expect(arr).toBe(arr2); // Fails as references are not equal expect(arr).toBe([1, 2, 3]); }); });OutputThis ...
Read MoreWhat is the use of sentry in javascript?
Sentry is a complete javascript debugging and monitoring tool package that allows you to track your production code. Some of the features of sentry −Record environment and usage details to recreate and fix bugsSee the error and stack trace previously only visible in user's debug console.Apply source maps automatically to convert minified, compiled, or transpiled code back to its original form.Mobile app reporting support.
Read MoreDifference between application/x-javascript and text/javascript content types?
The text/javascript content type is obsolete. This was used in the early days of Html.application/x-javascript was an experimental content type(hence the x-). You should not be using this in your application.The correct content type to use in browsers is application/javascript. This helps browsers accept the content as js code.
Read MoreWhat is the replacement of lodash pluck() method?
Pluck has been removed from lodash 4. This is because it did the same thing as a map.As a replacement, you can use the map function in the following way −Exampleimport _ from 'lodash' const objects = [{ 'a': 1 }, { 'a': 2 }]; console.log(_.map(objects, 'a'))OutputThis will give the output −[1, 2]
Read MoreWhere is _.pluck() in lodash version 4?
Pluck has been removed from lodash 4. This is because it did the same thing as a map.As a replacement, you can use the map function in the following way −Exampleimport _ from 'lodash' const objects = [{ 'a': 1 }, { 'a': 2 }]; console.log(_.map(objects, 'a'))This will give the output −Output[1, 2]
Read MoreWhy doesn't JavaScript support multithreading?
JavaScript used to be single-threaded. It runs using what is called an event loop.The Event Loop has one simple job — to monitor the Call Stack and the Callback Queue. If the Call Stack is empty, it will take the first event from the queue and will push it to the Call Stack, which effectively runs it.JS in browsers doesn't support multithreading in the event loop as it is not needed for 99.999% of the websites. The event loop handles everything seamlessly.For the remaining apps, devs can use web workers. Web Workers are a simple means for web content to ...
Read MoreHow to test if a letter in a string is uppercase or lowercase using javascript?
To test if a letter in a string is uppercase or lowercase using javascript, you can simply convert the char to its respective case and see the result.Examplefunction checkCase(ch) { if (!isNaN(ch * 1)){ return 'ch is numeric'; } else { if (ch == ch.toUpperCase()) { return 'upper case'; } if (ch == ch.toLowerCase()){ return 'lower case'; } } } console.log(checkCase('a')) console.log(checkCase('A')) console.log(checkCase('1'))OutputThis will give the output −lower case upper case ch is numeric
Read MoreWhat Is a JavaScript Framework?
JS frameworks are JavaScript code libraries that have pre-written code to use for routine programming features and tasks. It is literally a framework to build websites or web applications around.For example, in plain JS, you have to manually update the DOM using DOM APIs for setting styles updating content, etc.JS frameworks can help automate this repetitive task using features like 2-way binding and templating.Frameworks have their own way of doing things. For example, Angular is a popular JS framework that comes with many features like dependency injection, routing, etc and has its own way of building an application using it. ...
Read MoreHow to get a subset of a javascript object's properties?
To get a subset of object's properties and create a new object out of those properties, use object destructuring and property shorthand. For example, You have the following object −Exampleconst person = { name: 'John', age: 40, city: 'LA', school: 'High School' }And you only want the name and age, you can create the new objects using −const {name, age} = person; const selectedObj = {name, age}; console.log(selectedObj);OutputThis will give the output −{ name: 'John', age: 40 }
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