Documentation

Student-friendly HTML, CSS, and JavaScript reference with examples

Sections


                                        code & data


                                        input & output


                                        data types


                                        math


                                        > < === !==


                                        && || !


                                        undefined vs null vs ""

Types of Data

"Ada", 42, true

Data comes in different kinds, and code treats each kind differently.

"Ada"      // text — a string
42         // a number
true       // yes/no — a boolean

Text (Strings)

Wrapped in quotes: "hello", "Ada Lovelace", "42" — yes, even digits in quotes are
text, not a number.

Numbers

No quotes: 42, -7, 3.14.

Booleans

Only two possible values: true or false. Nothing in between.

Why the Type Matters

"5" + "5"   // "55" — text glued together
5 + 5       // 10  — actual math

Same symbol, +, completely different result — because the type is different.

Lessons 0/10

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○ What Type Is It? #1 guess_type ○ What Type Is It? #2 guess_type ○ What Type Is It? #3 guess_type ○ What Type Is It? #4 guess_type ○ What Type Is It? #5 guess_type ○ What Type Is It? #6 guess_type ○ What Type Is It? #7 guess_type ○ What Type Is It? #8 guess_type ○ What Type Is It? #9 guess_type ○ What Type Is It? #10 guess_type