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JavaScript Keywords That Every Experienced Web Developer Should Know

Shalitha Suranga 33

Photo by James Harrison on Unsplash, edited with Canva

Every programming language typically comes with developer-productivity-focused grammar and a fully-featured standard library. A generic programming language grammar specification contains several elements, such as literals, identifiers, expressions, functions, classes, etc. These elements typically use reserved words known as keywords that we can’t use for custom identifiers. Most developers don’t tend to learn all language keywords while learning a new programming language — but knowing all keywords of a particular language enhances your language mastery and boosts your productivity during programming.

Modern JavaScript has about 46 reserved, implemented keywords and several unimplemented reserved ones. Some of them came with early JavaScript implementations, and current ECMAScript specifications introduced several new keywords too. Every programmer usually knows about keywords like if, else, return, for, while, and function, but there are some keywords that we don’t frequently use as previously mentioned basic ones.

In this story, I’ll discuss some JavaScript keywords that you should know as an experienced JavaScript developer. Knowing these keywords apart from well-known keywords will help to write clean JavaScript code productively without spending time on technical forums. Also, experienced developers can use these keywords to test the JavaScript language experience of other developers during technical interviews. Moreover, these keywords motivate you to study JavaScript internals deeply.


We frequently use JavaScript objects in our source codes, so manipulating objects becomes mandatory in JavaScript environments. Adding and modifying object properties is so easy with the generic . notation. The delete keyword helps you remove a specific property from a JavaScript object:

let doc = {
id: 100,
title: 'My document',
size: 'A4',
notes: ''

delete doc.notes;

console.log(Object.keys(doc).length); // 3

Deleting an array element won’t affect the array size, but it empties the selected element, so you have to…