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What Is JavaScript Used For?
JavaScript adds interactivity to websites and also powers servers, apps, and tools.
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AiTechWorlds
AiTechWorlds
JavaScript is the programming language of the web, running in every browser. This visual guide covers JavaScript essentials: variables, functions, arrays, objects, the DOM, closures, promises, async/await, and the event loop.
JavaScript adds interactivity to websites and also powers servers, apps, and tools.
Use const by default, let when reassigning, and avoid var in modern code.
Core types include string, number, boolean, null, undefined, object, and symbol.
Functions group logic; arrow functions are a shorter syntax that keeps the outer this.
Arrays hold ordered lists with methods like push, map, filter, and reduce.
Objects store data as key–value pairs and can hold functions called methods.
The DOM is the browser’s tree of page elements that JavaScript can read and change.
Event listeners run code in response to user actions like clicks and key presses.
this refers to the object that is calling the current function, and its value depends on context.
Scope controls variable access; a closure lets a function remember variables from where it was created.
A callback is a function passed to another function to run later, often after async work.
A promise represents a future value from an async operation that may resolve or reject.
async/await writes asynchronous code that reads like synchronous, step-by-step code.
The event loop lets single-threaded JavaScript handle async tasks without blocking.
map transforms, filter selects, and reduce combines array items into a single value.
Spread (...) expands arrays/objects; rest collects multiple arguments into one array.
Destructuring pulls values out of arrays and objects into variables in one line.
Modules split code into files you can import and export for reuse.
Watch for == vs ===, hoisting surprises, and mutating shared state.
JSON is a text data format; fetch() makes HTTP requests to APIs and returns promises.
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