10+ Centum Learning Interview Questions and Answers

The return type of getElementsByClassName method in JavaScript is an array of elements.

• The method returns an array of elements that have a specified class name.

• The elements are returned in the order they appear in the document.

• If no elements are found with the specified class name, an empty array is returned.

Javascript is single-threaded.

• Javascript runs on a single thread called the event loop.

• This means that it can only execute one task at a time.

• However, it can delegate tasks to other threads using web workers.

• This allows for parallel processing without blocking the main thread.

JavaScript data types include string, number, boolean, object, function, undefined, and null.

• String: 'hello'

• Number: 42

• Boolean: true or false

• Object: { key: 'value' }

• Function: function() { }

• Undefined: undefined

• Null: null

Async/Await is a feature in JavaScript that allows for easier handling of asynchronous code.

• Async/Await is built on top of Promises and provides a more readable and concise way to work with asynchronous code.

• The 'async' keyword is used to define a function as asynchronous, allowing the use of 'await' inside it to pause execution until a Promise is settled.

• Using Async/Await can help avoid callback hell and make code more maintainable and easier to understand.

• Example: async fun...read more

typeof() operator in JavaScript is used to determine the data type of a variable or expression.

• typeof() returns a string indicating the type of the operand.

• Example: typeof 42 will return 'number'.

• Example: typeof 'hello' will return 'string'.

Data can be shared between components in Angular using services, input/output properties, and observables.

• Use services to create a shared data service that can be injected into multiple components

• Use input/output properties to pass data from parent to child components

• Use observables to create a data stream that can be subscribed to by multiple components

Types of data binding in Angular include interpolation, property binding, event binding, two-way binding.

• Interpolation: {{ data }}

• Property binding: [property]="data"

• Event binding: (event)="function()"

• Two-way binding: [(ngModel)]="data"

JavaScript is single-threaded.

• JavaScript is single-threaded, meaning it can only execute one piece of code at a time.

• This is because JavaScript runs in the browser's main thread, which is responsible for handling user interactions, rendering, and running JavaScript code.

• Asynchronous operations in JavaScript, such as AJAX requests and setTimeout, allow for non-blocking code execution without the need for multi-threading.

• Web Workers can be used to run JavaScript code in the bac...read more

Position relative is relative to its normal position, while position absolute is relative to its nearest positioned ancestor.

• Position relative moves an element relative to its normal position.

• Position absolute moves an element relative to its nearest positioned ancestor.

• Position absolute elements are taken out of the normal flow of the document.

The typeof() method in JavaScript returns the data type of a variable or expression.

• typeof() returns a string indicating the type of the operand.

• It can be used with variables, literals, or expressions.

• Common return values include 'number', 'string', 'boolean', 'object', 'function', and 'undefined'.

z index determines the stacking order of elements on a webpage.

• z index is a CSS property that specifies the stack order of an element

• Elements with a higher z index value will be displayed on top of elements with a lower value

• Default z index value is 0, negative values are allowed

• z index only works on positioned elements (position: relative, absolute, fixed)

Async/await is a syntax for writing asynchronous code in a synchronous way.

• Async/await is built on top of Promises.

• Async functions always return a Promise.

• Await can only be used inside an async function.

• Async/await makes code easier to read and write compared to using callbacks or Promises.