Module 1 · JavaScript Fundamentals

History of JavaScript

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HistoryECMAScriptFundamentals

Introduction

JavaScript was created by Brendan Eich at Netscape in 1995, reportedly in about ten days. It was first called Mocha, then LiveScript, and finally JavaScript — a marketing decision to ride the popularity of Java, even though the two languages are unrelated.

Understanding this history explains many of the language's quirks (== coercion, typeof null === 'object', hoisting) and why the language has evolved so aggressively since 2015.

Why This Matters

Interviewers rarely ask for exact dates, but they do probe whether you understand why JavaScript behaves the way it does. Knowing the timeline lets you answer follow-ups like "why does let exist if we already had var?" or "what changed in ES6?" with confidence instead of guesses.

Theory

The timeline that matters

1995 — Brendan Eich builds the first version at Netscape in ~10 days.
1996 — Microsoft ships JScript in Internet Explorer, creating two incompatible dialects.
1997 — The language is standardised as ECMAScript (ECMA-262) to end the fragmentation.
2009 (ES5) — Strict mode, JSON, array methods (map, filter, reduce), getters/setters.
2015 (ES6 / ES2015) — The turning point: let/const, arrow functions, classes, promises, modules, destructuring, template literals. From here, a new spec ships every year.
2016+ — Yearly editions (ES2016…ES2023) add smaller, focused features (async/await, optional chaining, nullish coalescing, Array.flat, top-level await).

Why the quirks exist

Because the first version shipped in days and then had to stay backwards compatible forever ("don't break the web"), early mistakes could never be removed — only worked around. That is why we have let (to fix var), === (to fix ==), and modules (to fix implicit globals).

Visual Diagrams

JavaScript evolution at a glance

1995        1997         2009          2015              2016 -> now
 |           |            |             |                  |
Mocha ---> ECMAScript --> ES5 --------> ES6 (ES2015) -----> yearly editions
(Netscape)  (standard)   (strict mode) (let/const, class,   (async/await,
                          JSON, map)    promises, modules)   optional chaining)

One rushed prototype became a standardised language with a yearly release cadence.

Interview Questions

1Why is JavaScript named 'JavaScript' if it has nothing to do with Java?

It was a marketing decision. In 1995 Java was extremely popular, so Netscape rebranded LiveScript as JavaScript to benefit from the association. The languages share some C-like syntax but differ fundamentally: JavaScript is dynamically typed, prototype-based, and single-threaded with an event loop, whereas Java is statically typed and class-based.

Asked at:AmazonMicrosoft

2What was the single most important release in JS history?

ES6 (ES2015). It introduced let/const, arrow functions, classes, template literals, destructuring, default/rest/spread, promises, and native modules. It also began the yearly release cadence. Nearly every modern codebase is written in ES6+.

Quiz

1. Who created JavaScript and in which year?

Summary

JavaScript was created by Brendan Eich at Netscape in 1995.
It was standardised as ECMAScript (ECMA-262) in 1997 to stop browser fragmentation.
ES6 (2015) was the watershed release and began a yearly cadence.
Backwards compatibility ("don't break the web") is why the language's early quirks still exist.