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JavaScript Functions
function addTax(price, rate) {
const tax = price * rate;
return price + tax;
}
const total = addTax(100, 0.1);
console.log(total);Output → 110
Topics
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Structure and style your first web pages.
JSVariables, functions, loops and the DOM.
⚛Build interfaces from small components.
NPages, routing and full-stack React apps.
PHPServer-side code and web applications.
▲Build mobile apps for Android and iOS from one codebase.
DBStore and query data in a database.
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Each lesson explains one small concept in plain language, in about five minutes.
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New
Every web page starts with the same skeleton: a doctype, an html element, a head for information about the page, and a body for what people see.
Selectors tell CSS which HTML elements to style: by tag name, by class, or by id.
Variables are named boxes that store values. Use const for values that won't be reassigned and let for ones that will.
A function is a reusable block of code. You give it inputs, it does some work, and it can give a value back with return.
Arrays store a list of values in order. Each item has a numbered position called an index, starting at 0.
A React component is a JavaScript function that returns UI. You build pages by combining small components.
Lesson preview
Every lesson has learning objectives, a code example with its expected output, and the mistakes beginners usually make.
A function is a reusable block of code. You give it inputs, it does some work, and it can give a value back with return.
function addTax(price, rate) {
const tax = price * rate;
return price + tax;
}
const total = addTax(100, 0.1);
console.log(total);Expected output
110
Common mistake: Forgetting return
Without return the function gives back undefined, so total would be undefined instead of 110.
Quiz preview
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Roadmaps put lessons in order, so you always know your next step.
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Lesson: JavaScript FunctionsWhat does return mean in this function?
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