ECMAScript Interview Questions and Answers

ECMAScript Interview Questions and Answers


ECMA stands for European Computer Manufacture Association. ECMAScript (ES) is a scripting language specification standardized by ECMAScript International in ECMA-262 and ISO/IEC 16262. It was created to standardize JavaScript, so as to foster multiple independent implementations. JavaScript has remained the best-known implementation of ECMAScript since the standard was first published, with other well-known implementations including JScript and ActionScript. Coders commonly use ECMAScript for client-side scripting on the World Wide Web, and it is increasingly being used for writing server applications and services using Node.js. There are eight editions of ECMA-262 published. Present Work on version 8 of the standard was finalized in June 2017. ECMAScript provides the rules, details, and guidelines that a scripting language must observe to be considered ECMAScript compliant.

ECMAScript: A language standardized by ECMA International and overseen by the TC39 committee. This term is usually used to refer to the standard itself. Sun (now Oracle) had a trademark on the name “JavaScript” (Microsoft calling its JavaScript dialect “JScript”). Thus, when it came to standardizing the language, a different name had to be used. Instead, “ECMAScript” was chosen, because the corresponding standard is hosted by Ecma International. In practice, the terms “ECMAScript” and “JavaScript” are interchangeable. If JavaScript means “ECMAScript as implemented by Mozilla and others” then the former is a dialect of the latter. The term “ECMAScript” is also frequently used to denote language versions.

ECMAScript is a collection of built-in objects which round out the definition of ECMAScript entities. These built-in objects include the Global object, the Object, the Function object, the Array object, the String object, the Boolean object, the Number object, the Math object, and the Date object.

ECMAScript also a set of built-in operators which may not be, strictly speaking, functions or methods. ECMAScript operators include various unary operations, multiplicative operators, additive operators, bitwise shift operators, relational operators, equality operators, binary bitwise operators, binary logical operators, assignment operators, and the comma operator.

ECMAScript syntax intentionally resembles Java syntax. ECMAScript syntax is relaxed to enable it to serve as an easy-to-use scripting language. For example, a variable is not required to have its type declared nor are types associated with properties, and defined functions are not required to have their declarations appear textually before calls to them.

ECMA-262: The Ecma International (a standards organization) has created the ECMA-262 standard which is the official specification of the ECMAScript language.

ECMAScript 5 (ES5): The 5th edition of ECMAScript, standardized in 2009. This standard has been implemented fairly completely in all modern browsers.

ECMAScript 6 (ES6)/ ECMAScript 2015 (ES2015): The 6th edition of ECMAScript, standardized in 2015. This update adds significant new syntax for writing complex applications, including classes and modules, but defines them semantically in the same terms as ECMAScript 5 strict mode. Other new features include iterators and for/of loops, Python-style generators and generator expressions, arrow functions, binary data, typed arrays, collections (maps, sets and weak maps), promises, number and math enhancements, reflection, and proxies (metaprogramming for virtual objects and wrappers).

ECMAScript 7(ES7): The 7th edition of ECMAScript 2016, was finalized in June 2016.New features include the exponentiation operator (**), Array. Prototype. includes (not to be confused with ClassList.contains).

ECMAScript 8(ES8): The 8th edition of ECMAScript 2017, was finalized in June includes await/async, which works using generators and promises.

What is ECMAScript?

What is the relationship between JavaScript and ECMAScript?

What is Babel?

What is a Promise?

What is Webpack?

What is Traceur?

What is Reflect API?

What are the new features of ES6?

What are template literals in Es6?

What is Destructuring?

How to create a JavaScript class in ES6?

What is the ES6 Map feature?

What are the new feature of ES7?

What are the new features of ES8?

What is BabelJS?

What are the benefits of using Webpack?

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