The Simple Notes About What Is Javascript and How It Works, From Legacy to Modern

The Simple Notes About What Is Javascript and How It Works, From Legacy to Modern

Javascript is one of the most language for web development nowadays.

Javascript is one of the most language for web development nowadays. It has a complicated history with both up and down trend, with many subsets, extensions … which could make beginners misunderstood the core concept behind this powerful language, and I am one of them. So, I decided to research and try to comprehend the fundamentals before go deeper with advanced tools such as frameworks or libraries. This post is more like my personal notes, which have been documented from many sources to have a clear and concise overview about Javascript. (Feel free to correct me if I wrote anything wrong, much appreciated. )

The History

The 1990s was the period when internet have been adopted and many important technologies were created. At that Tim, two dominant browsers are Netscape’s Navigator and Microsoft’s Internet Explorer, with the well-know legal battle lately. In September 1995, Brandan Eich, a Netscape programmer, developed a new scripting language in just 10 days. It was originally named Mocha, then LiveScript and, finally, JavaScript.

The Standards

In 1997, JavaScript has been adopted rapidly, it’s obvious that the language would need to be properly maintained and standardized. Therefore, Netscape handed the job of building a language specification to the European Computer Manufacturers Association (ECMA), an organization founded with the goal of standardizing computing. The ECMA specifications were labeled ECMA-262 and ECMAScript languages included JavaScript, JScript, and ActionScript.

ECMA-262 had three revisions from 1997 to 1999, but nearly 10 years later, version 4 was abandoned due to disagreements on the direction of the language and features. Many of modern features, such as generators, iterators, and destructuring assignments, arrow function, classes … have been included in more recent ECMAScript specifications. The latest edition is 11th, officially known as ECMAScript 2020, was published in June 2020. One of the features of ECMAScript 2020 is the nullish coalescing operator, ??, returns its right-hand side operand when its left-hand side is null or undefined. This contrasts with the || operator, which uses the right value if left-hand side is falsy

console.log(true ?? "not defined") // true
console.log(false ?? "not defined") // false
console.log(undefined ?? "not defined") // "not defined"
console.log(null ?? "not defined") // "not defined"

//Compared with the OR operator ||
console.log(true || "not defined") // true
console.log(false || "not defined") // "not defined"
console.log(undefined || "not defined") // "not defined"
console.log(null || "not defined") // "not defined"


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