Boolean

A Boolean has one of two possible values: true or false. Boolean (logical) operators (and, or, not) take Boolean inputs and make another Boolean value. Comparison operators on other types (numbers, strings) create Boolean values.

These blocks represent the true and false Boolean values, which can plug into anyplace a Boolean value is expected:

let on = true;

The next three blocks represent the three Boolean (logic) operators:

let and = true && false;
let or = true || false;
let not = !true;

The next six blocks represent comparison operators that yield a Boolean value. Most comparisons you will do involve numbers:

let equality = 42 == 42;
let inequality = 42 != 42;
let lowerThan = 42 < 0;
let greaterThan = 42 > 0;
let lowerOrEqualThan =42 <= 0;
let greaterOrEqualThan = 42 >= 0;

Boolean values and operators are often used with an if or while statement to determine which code will execute next. For example:

let a = 5
let b = 87

if (a < b) {
a += 1
}

while (a < b) {
a += 1
}

Functions that return a Boolean

Some functions return a Boolean value, which you can store in a Boolean variable. For example, the following code gets the on/off state of point (1, 2) and stores this in the Boolean variable named on. Then the code clears the screen if on is true:

Boolean operators

Boolean operators take Boolean inputs and evaluate to a Boolean output:

Conjunction: A and B

A and B evaluates to true if-and-only-if both A and B are true:

let off = false && false;
let off2 = false && true;
let off3 = true && false;
let on = true && true;

Disjunction: A or B

A or B evaluates to true if either A is true or B is true, or if both A and B are true:

let off = false || false;
let on = false || true;
let on2 = true || false;
let on3 = true || true;

Negation: not A

not A evaluates to the opposite (negation) of A:

let on = !false;
let off = !true;