Certainly, here are 100 JavaScript terms along with brief explanations:

1. JavaScript (JS): A high-level, interpreted programming language.
2. ECMAScript: The standard upon which JavaScript is based.
3. Variable: A container for storing data values.
4. Data Types: The classifications of data, including String, Number, and Boolean.
5. String: A sequence of characters, enclosed in quotes.
6. Number: A numerical data type.
7. Boolean: A data type representing true or false values.
8. Array: An ordered collection of values.
9. Object: A collection of key-value pairs.
10. Function: A reusable block of code.
11. Operator: A symbol that performs an operation on one or more operands.
12. Conditional Statements: Statements that execute based on a condition.
13. Loops: Constructs for repeating code execution.
14. Event: An action or occurrence recognized by the program.
15. DOM (Document Object Model): A programming interface for web documents.
16. HTML: HyperText Markup Language.
17. CSS: Cascading Style Sheets.
18. JSON (JavaScript Object Notation): A lightweight data interchange format.
19. AJAX (Asynchronous JavaScript and XML): A technique for asynchronous data retrieval.
20. Callback: A function passed as an argument to another function.
21. Scope: The context in which variables exist.
22. Closure: A function with access to its own scope, and the outer function's scope.
23. Prototype: An object used as a template for other objects.
24. Inheritance: The ability of an object to inherit properties and methods from another object.
25. Constructor: A function used to create and initialize objects.
26. this Keyword: Refers to the current object.
27. Arrow Function: A concise way to write functions in ES6.
28. Promise: Represents the eventual completion or failure of an asynchronous operation.
29. Async/Await: Keywords for handling asynchronous code.
30. Fetch API: A modern interface for fetching resources asynchronously.
31. Error Handling: Managing and responding to errors in code.
32. Strict Mode: A mode that catches common coding errors.
33. Module: A reusable piece of code that encapsulates related functionality.
34. IIFE (Immediately Invoked Function Expression): A function that is executed immediately after being created.
35. Babel: A JavaScript compiler for converting ES6+ code to ES5.
36. npm (Node Package Manager): A package manager for JavaScript.
37. Node.js: A server-side JavaScript runtime.
38. Express.js: A web application framework for Node.js.
39. Vue.js: A progressive JavaScript framework for building user interfaces.
40. React: A JavaScript library for building user interfaces.
41. Angular: A web application framework.
42. JSX (JavaScript XML): Syntax extension for JavaScript recommended with React.
43. TypeScript: A superset of JavaScript that adds static typing.
44. ES6 (ECMAScript 2015): Major update to JavaScript, introducing new features.
45. ESNext: The upcoming version of ECMAScript.
46. Destructuring: Extracting values from objects or arrays.
47. Spread Operator: Expands elements of an array or properties of an object.
48. Rest Parameter: Gathers remaining arguments into an array.
49. Map: A collection of key-value pairs with iterable methods.
50. Set: A collection of unique values.
51. WeakMap: A collection of key-value pairs where keys are objects.
52. WeakSet: A collection of unique objects.
53. Proxy: An object used for custom behavior on another object.
54. Reflect: An object providing methods for reflection.
55. Promise.all(): Returns a promise that fulfills when all promises in an array are fulfilled.
56. Promise.race(): Returns a promise that fulfills or rejects as soon as one promise in an array fulfills or rejects.
57. Generator: A function that can be paused and resumed.
58. Iterator: An object implementing the iterator protocol.
59. Template Literal: Strings allowing embedded expressions.
60. Webpack: A module bundler for JavaScript applications.
61. ESLint: A tool for identifying and fixing problems in JavaScript code.
62. Jest: A JavaScript testing framework.
63. Unit Testing: Testing individual units or components of code.
64. Integration Testing: Testing the interaction between components.
65. Functional Testing: Testing the functionality of the entire system.
66. Jasmine: A behavior-driven development framework for testing JavaScript code.
67. Mocha: A JavaScript test framework.
68. Chai: A BDD/TDD assertion library.
69. Karma: A test runner for JavaScript.
70. Redux: A state management library for JavaScript applications.
71. Flux: An architecture for building scalable and maintainable web applications.
72. Middleware: Functions that have access to the request and response objects in Express.js.
73. Immutable.js: A library for working with immutable data structures.
74. WebSockets: A communication protocol providing full-duplex communication.
75. Local Storage: A web storage solution for storing data persistently.
76. Session Storage: A web storage solution similar to local storage but session-specific.
77. Cookies: Small pieces of data stored on the client's browser.
78. Canvas: An HTML element used for drawing graphics.
79. SVG (Scalable Vector Graphics): XML-based vector image format.
80. WebGL: A JavaScript API for rendering interactive 3D graphics.
81. Responsive Design: Designing web pages for optimal viewing on various devices.
82. Mobile-First Design: Design approach focusing on mobile devices first.
83. Progressive Web App (PWA): A type of application software delivered through the web.
84. Service Worker: A script that runs in the background, separate from a web page.
85. Cross-Origin Resource Sharing (CORS): Mechanism allowing or restricting web resources on different domains.
86. Same-Origin Policy: Security measure preventing web pages from making requests to a different domain.
87. Asynchronous Programming: Executing code without waiting for certain operations to complete.
88. Hoisting: JavaScript's default behavior of moving declarations to the top.
89. Event Delegation: Technique for handling events on parent elements.
90. XSS (Cross-Site Scripting): Security vulnerability allowing attackers to inject malicious scripts.
91. CSRF (Cross-Site Request Forgery): Security vulnerability where an attacker tricks the user into performing actions they did not intend.
92. Web Accessibility (A11y): Ensuring web content is accessible to all users.
93. SEO (Search Engine Optimization): Techniques to improve a website's visibility on search engines.
94. Single Page Application (SPA): Web application loading a single HTML page and dynamically updating the content.
95. Routing: Managing navigation in a web application.
96. SSR (Server-Side Rendering): Rendering web pages on the server before delivering them to the client.
97. CSR (Client-Side Rendering): Rendering web pages on the client side using JavaScript.
98. API (Application Programming Interface): A set of rules allowing different software applications to communicate with each other.
99. Microservices: Architectural approach where a software application is composed of small, independent services.
100. Design Patterns: Reusable solutions to common problems in software design.