JavaScript or JavaScript: Does Capitalisation Matter?

It's JavaScript, with a capital J and a capital S. "Javascript" is understandable, but I'd correct it in an article, a job description, or interface copy.

Mozilla's JavaScript introduction uses that spelling consistently. It's the name readers will recognise from the documentation.

That doesn't make "Javascript" a reliable test of someone's engineering ability. It may be a typo, a house‑style mistake, or text written by someone whose job isn't programming. Building a theory about the author from one letter is rather more ambitious than the evidence allows.

Where Ecmascript Fits

ECMAScript is the name used for the language standard published as ECMA‑262. JavaScript is the familiar language name used in implementations and everyday development.

The ECMAScript 2015 specification describes the standardised language, including its syntax, types, and built‑in objects. A browser supplies additional capabilities around that language, such as the document object model. A server environment supplies a different set of facilities.

In Code, Case Changes the Name

JavaScript identifiers are case‑sensitive. If a function parameter is named total, referring to Total does not automatically refer to the same binding. It may refer to another binding, or fail because no such name exists in the relevant scope.

The lexical grammar in the 2015 specification defines identifiers and reserved words precisely. Check the exact name before looking for a more elaborate explanation.