Basic data types

Numbers

Numbers are 8 byte, floating-point.

const i = 16;
const j = 38.53;
const z = i + j;
console.log(z); // -> 54.53

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54.53

Strings

Strings are Unicode.

let s = "my";
s = s + " message";
console.log(s); // -> my message

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my message

Arrays

Arrays can grow and shrink and elements can be of any type.

const cars = ["Model 3", "Leaf", "Bolt"];
console.log("first car:", cars[0]);

const mixedTypes = ["string"];
mixedTypes.push(5);
console.log("array with mixed types:", mixedTypes);

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first car: Model 3
array with mixed types: [ 'string', 5 ]

Objects (dictionaries, hash tables)

Objects map keys to values. In other languages they are known as dictionaries or hash tables. Values can be of any type, including functions.

const person = {
	firstName: "John",
	lastName: "Doe",
	log: () => console.log("hello from log()")
};
console.log("firstName:", person.firstName);
console.log("lastName:", person["lastName"]);
person.log();

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firstName: John
lastName: Doe
hello from log()

Functions

Functions are first-class meaning they can be assigned to variables and passed around.

const logMe = function(s) {
	console.log(s);
}
const logMe2 = logMe;
logMe2("hello");

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hello

Dynamic typing

The same variable can be assigned values of different types.

let v;
console.log(v);

v = 5;
console.log(v);

v = "str";
console.log(v);

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undefined
5
str

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