Who Invented JavaScript the Brendan Eich Story

Who invented JavaScript? Brendan Eich, an American programmer working at Netscape Communications, created it in May 1995. He wrote the first version of the language in just 10 days, under intense pressure to ship it fast.

That single fact -- 10 days -- explains a lot about JavaScript. It was not the product of years of careful language design. It was a prototype, built fast, that escaped into the wild and became the most widely used programming language in history.

The Context: The Browser Wars of 1995

In 1995, the web was new and mostly static. Pages were documents with text and images, connected by hyperlinks. The dominant browser was Netscape Navigator, and its main competitor was Microsoft's Internet Explorer.

Netscape wanted to add interactivity to web pages -- buttons that did something, forms that checked input, pages that changed without reloading. The browser needed a scripting language.

Two options were on the table:

• Scheme, a minimalist Lisp dialect that Eich favored
• Java, which Sun Microsystems was promoting as the future of web applets

Netscape management wanted something that looked like Java syntactically to ride Java's marketing wave, but was simpler and more accessible for designers and beginners. Eich was hired specifically to "write a Scheme-like language with Java syntax for the browser."

The 10-Day Sprint

In May 1995, Eich locked himself in a room and wrote the first JavaScript engine -- called SpiderMonkey -- in 10 days. The language he created borrowed:

The result was a language that looked familiar to Java programmers but behaved more like a functional scripting language underneath. This split personality -- C-like syntax with Lisp-like semantics -- is still visible in JavaScript today.

The Name: Mocha, LiveScript, JavaScript

The language went through three names in rapid succession:

The name "JavaScript" was a marketing decision. Sun Microsystems had just released Java, and it was generating enormous hype. Netscape made a licensing deal with Sun to use "JavaScript" as the name, hoping to make the new language sound like a lighter, friendlier version of Java.

This decision caused decades of confusion. Beginners constantly ask whether JavaScript and Java are related. They are not. The name is a branding artifact, not a technical connection.

What Happened After the 10 Days

Eich intended to refine JavaScript after the initial prototype. That never happened. Netscape Navigator 2.0 shipped with JavaScript in September 1995, and suddenly millions of people were writing code in a 10-day prototype.

Microsoft responded by reverse-engineering JavaScript and creating JScript for Internet Explorer 3.0 in 1996. To prevent the web from splitting into incompatible dialects, Netscape submitted JavaScript to Ecma International for standardization in 1997. This became ECMAScript -- the official standard that JavaScript engines still follow today.

Brendan Eich After JavaScript

Eich stayed with Netscape through its acquisition by AOL, then co-founded the Mozilla Foundation in 2003. At Mozilla, he helped create Firefox and served as CTO and briefly as CEO.

In 2014, Eich left Mozilla and co-founded Brave Software, which makes the Brave browser -- a privacy-focused browser that blocks ads and trackers by default. He also created the Basic Attention Token (BAT), a cryptocurrency-based digital advertising system.

Today, Eich is no longer directly involved in JavaScript's standardization through TC39, but the language he created in 10 days now runs on over 98% of the world's websites.

Why the 10-Day Origin Matters

Knowing that JavaScript was built in 10 days helps explain some of its quirks:

• typeof null === "object" is a bug from the first version that was never fixed because too many websites depended on it
• Automatic semicolon insertion sometimes produces surprising results
• The == operator's type coercion rules are complex and inconsistent

These are not design flaws from careful deliberation. They are artifacts of a prototype that shipped too fast and became too widely used to fix. Understanding this makes JavaScript's quirks less frustrating -- they are historical fossils, not incompetence.

For the full timeline of what happened after those 10 days, read about the complete history of JavaScript. If you are new to the language entirely, start with what JavaScript is and why it matters.