Variables & Data Types

Declaring Variables

Variables are containers for storing data values. In modern JavaScript, we use let and const:

// let - for values that can change
let bpm = 128;
bpm = 130; // OK - we can change it

// const - for values that won't change
const sampleRate = 44100;
// sampleRate = 48000; // ERROR - can't reassign const

// var - old way (avoid using)
var oldWay = "don't use this";

Data Types

Working with Data

// Numbers
let bpm = 128;
let duration = 240; // seconds
let energy = 0.85;

// Strings
let title = "Summer Nights";
let artist = 'DJ Mix';
let message = `BPM: ${bpm}`; // Template literal

// Booleans
let isPlaying = false;
let hasAnalysis = true;

// Arrays
let tracks = ["song1.mp3", "song2.mp3", "song3.mp3"];
console.log(tracks[0]); // "song1.mp3"

// Objects
let track = {
    title: "Summer Nights",
    bpm: 128,
    key: "Am",
    duration: 240
};
console.log(track.title); // "Summer Nights"

// Storing audio analysis results
const analysisResult = {
    bpm: 128,
    key: "Am",
    energy: 0.85,
    sections: [
        { start: 0, end: 30, type: "intro" },
        { start: 30, end: 90, type: "verse" }
    ]
};

// Storing track metadata
let currentTrack = {
    file: audioFile,
    buffer: audioBuffer,
    analysis: analysisResult
};