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javascript Interview Questions
basics
What are the key features of JavaScript?
JavaScript is a high-level, interpreted programming language commonly used for web development. Key features include dynamic typing, first-class functions, event-driven programming, support for asynchronous operations (like Promises and async/await), and the ability to manipulate the DOM (Document Object Model) in web pages.
What is the difference between `var`, `let`, and `const` in JavaScript?
`var` has function scope and can be redeclared or updated, potentially leading to issues. `let` is block-scoped and can be updated but not redeclared within the same scope. `const` is also block-scoped and cannot be updated or redeclared, ensuring constant values.
dom
What is the Document Object Model (DOM) in JavaScript?
The DOM is a programming interface for web documents that represents the page as a tree structure of nodes, allowing scripts to update the content, structure, and style of a document. JavaScript can be used to manipulate the DOM by selecting elements, modifying attributes, and reacting to user events.
es6
What are the key features introduced in ES6?
ES6 introduced several new features such as `let` and `const` for block-scoped variable declarations, arrow functions, template literals, destructuring assignment, default parameters, `Promise` for asynchronous code, classes, modules, and the spread/rest operators (`...`).
What are template literals in ES6?
Template literals allow for multi-line strings and embedded expressions. They are created using backticks (`` ` ``) instead of quotes. For example: ```js const name = 'John'; const greeting = `Hello, ${name}!`; ```
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