Expressions

Functions

`function` Function expression.

function identifier ( parameter list ) compound statement
function identifier compound statement

Defines function with a specified name and optional aliases for arguments.

function ( parameter list ) compound statement
function compound statement

Defines function with optional aliases for arguments.

`=>` "Fat arrow" function expression.

( parameter list ) => compound statement

Defines function with aliases for arguments.

( parameter list ) => statement

Defines function with aliases for arguments. The return value of the function is the value of an expression that the statement consists of.

JSON expression.

A sequence of JSON statements between braces.

Warning

Probably not fully compatible with JSON specification yet.

Classes

`class` expression.

class identifier json-expression
class identifier extends identifier json-expression

Defines a new class (Class object) optionally with a specified base class.

Declarations

`let` expression.

let identifier

Declares variable with the specified name. The default value is Object().

Operators

Notation

Warning

In this document the following notation is used:a["operator"](b) (where operator can be +, -, ==, await …). However, read operator (a["property"]) can be overloaded (e.g. Array overloads this operator), and the intended behavior is as following:

Object.classPrototype.readOperator.call(a, "operator")(b)

Arithmetic Operators

a + b Addition operator.

If a is a Number and b is convertible to Number, then operator adds them. If a is a String and b is convertible to String, then operator concatenates them. If a is an Array and b is convertible to Array, then operator merges them. Otherwise, operator calls a["+"](b).
a - b Subtraction operator.

If a is a Number and b is convertible to Number, then operator subtracts the second operand from the first. Otherwise, operator calls a["-"](b).
a * b Multiplication operator.

If a is a Number and b is convertible to Number, then operator multiplies them. If a is a String and b is convertible to Number, then operator concatenates b copies of a (e.g. "ab" * 2 is "abab"). If a is an Array and b is convertible to Number, then operator merges b copies of a Otherwise, operator calls a["*"](b).
a / b Division operator.

If a is a Number and b is convertible to Number, then operator divides the first operand by the second. Otherwise, operator calls a["/"](b).
a % b Modulo operator.

If a is a Number and b is convertible to Number, then operator finds the remainder after division of the first operand by the second, both operands are rounded downward before operation. Otherwise, operator calls a["%"](b).
a++ Increment operator.

If a is a Number and b is convertible to Number, then operator increments the operand. Otherwise, operator calls a["++"]().
a-- Decrement operator.

If a is a Number and b is convertible to Number, then operator decrements the operand. Otherwise, operator calls a["--"]().

Relational Operators

a == b Equality operator.

If a is of type T and b is convertible to type T, then operator checks if the values of two operands are equal (where T is Number, String, Array or Boolean). Otherwise, operator calls a["=="](b).
a is b Identity operator.

Checks if the operands refer to the same object. Equivalent of a.getId() == b.getId().
a != b Inquality operator.

If a is of type T and b is convertible to type T, then operator checks if the values of two operands are not equal (where T is Number, String, Array or Boolean). Otherwise, operator calls a["!="](b).
a > b Greater than operator.

If a is of type T and b is convertible to type T, then operator checks if the value of the first operand is greater than the value of the second operand (where T is Number, String or Array or Boolean). Otherwise, operator calls a[">"](b).
a >= b Greater than or equal operator.

If a is of type T and b is convertible to type T, then operator checks if the value of the first operand is greater or equal than the value of the second operand (where T is Number, String or Array or Boolean). Otherwise, operator calls a[">="](b).
a < b Less than operator.

If a is of type T and b is convertible to type T, then operator checks if the value of the first operand is less than the value of the second operand (where T is Number, String or Array or Boolean). Otherwise, operator calls a["<"](b).
a <= b Less than or equal operator.

If a is of type T and b is convertible to type T, then operator checks if the value of the first operand is less or equal than the value of the second operand (where T is Number, String or Array or Boolean). Otherwise, operator calls a["<="](b).

Logical Operators

a && b Logical AND operator.

If a is convertible to Boolean and b is convertible to Boolean, then operator is true if both of its operands are true and false if at least one operand is false. Otherwise, operator calls a["&&"](b).
a || b Logical OR operator.

If a is convertible to Boolean and b is convertible to Boolean, then operator is a if the first operand is true and b otherwise. Otherwise, operator calls a["||"](b).
!a Logical NOT operator.

If a is convertible to Boolean, then operator negates the value of the operand. Otherwise, operator calls a["!"]().

Bitwise Operators

a & b Binary AND operator.

If a is a Number and b is convertible to Number, then operator puts a 1 bit in each bit position if it exists in this position in both operands. Otherwise, operator calls a["&"](b).
a | b Binary OR operator.

If a is a Number and b is convertible to Number, then operator puts a 1 bit in each bit position if it exists in this position in at least one operand. Otherwise, operator calls a["|"](b).
a ^ b Binary XOR operator.

If a is a Number and b is convertible to Number, then operator puts a 1 bit in each bit position if it exists in this position in exactly one operand. Otherwise, operator calls a["^"](b).
a << b Binary left shift operator.

If a is a Number and b is convertible to Number, then operator shifts the value of the first operand to the left by the number of bits specified by the second operand. Otherwise, operator calls a["<<"](b).
a >> b Binary right shift operator.

If a is a Number and b is convertible to Number, then operator shifts the value of the first operand to the right by the number of bits specified by the second operand. Otherwise, operator calls a["<<"](b).
~a Binary complement operator.

If a is Number, then operator flips the bits of its operand. Otherwise, operator calls a["~"]().

Assignment Operators

a = b Assignment operator.

If a is not a constant assign the copy of b to a.
a <- b Initialization assignment operator.

If a is in form identifier, expression.identifier or let identifier, then operator makes a a reference to b (a and b points to the same object).
a : b JSON assignment operator.

If a is identifier, then operator creates variable a and assign b to it (if b is constant, assign copy of b). If a is String, then operator creates variable with a value of a as name and assign b to it (if b is constant, assign a copy of b).

Call operators

f(/* ... */) Call operator.

If f is instance of Function calls f, otherwise if f.callOperator exists calls it.
x.m(/* ... */) Method call operator.

If x.m is instance of Function calls x.m, otherwise if x.m.callOperator exists calls it.
a[b] Read operator.

Equivalent of a.readOperator(b).
a @f@ b Binary function operator.

Equivalent of f(a, b).
@f a Decorator.

Equivalent of f(a).

Other operators

...a Spread operator
- f(...a) Function call, method call and read operator.
If a is convertible to Array, pass elements of the array to the function. Example:
```
console.log(1, 2, ...[3, 4], 5, 6);
```
- { ...a } Object literal.
Pass properties of a (excluding prototype) to the new object. Example:
```
{ x: 1, ...{ y: 2, z: 3 } }
```
- [ ...a ] Array literal.
If a is convertible to Array, pass elements of the array to new array. Example:
```
[1, 2, ...[3, 4], 5, 6]
```
- ...a Stack.
Unpack properties of a as variables. Example:
```
let a = { x: 1, y: "abc" }
// console.log(y) Error: "y not found"
...a
console.log(y) // Prints "abc"
```
a ? b : c Conditional (ternary) operator.

If a is true then value of conditional expression is b, otherwise it's c.
start..stop or start..stop..step Range operator.

Creates range. Example:
```
for (let i in 0..10)
    console.log(i);
```
a instanceOf b "Instance of" operator.

Checks if b is an instance of a (if a has b.classPrototype in its prototype chain).
delete a Delete operator.

If a is identifier, then operator deletes variable a. If a is expression.identifier, then operator deletes that property.
await a Await operator.

Equivalent of a["await"]().
a.b Dot operator.

Provides access to properties of object. Equivalent of a["b"].

Expressions

Functions

function Function expression.

=> "Fat arrow" function expression.

JSON expression.

Classes

class expression.

Declarations

let expression.

Operators

Notation

Arithmetic Operators

a + b Addition operator.

a - b Subtraction operator.

a * b Multiplication operator.

a / b Division operator.

a % b Modulo operator.

a++ Increment operator.

a-- Decrement operator.

Relational Operators

a == b Equality operator.

a is b Identity operator.

a != b Inquality operator.

a > b Greater than operator.

a >= b Greater than or equal operator.

a < b Less than operator.

a <= b Less than or equal operator.

Logical Operators

a && b Logical AND operator.

a || b Logical OR operator.

!a Logical NOT operator.

Bitwise Operators

a & b Binary AND operator.

a | b Binary OR operator.

a ^ b Binary XOR operator.

a << b Binary left shift operator.

a >> b Binary right shift operator.

~a Binary complement operator.

Assignment Operators

a = b Assignment operator.

a <- b Initialization assignment operator.

a : b JSON assignment operator.

Call operators

f(/* ... */) Call operator.

x.m(/* ... */) Method call operator.

a[b] Read operator.

a @f@ b Binary function operator.

@f a Decorator.

Other operators

...a Spread operator

a ? b : c Conditional (ternary) operator.

start..stop or start..stop..step Range operator.

a instanceOf b "Instance of" operator.

delete a Delete operator.

await a Await operator.

a.b Dot operator.

`function` Function expression.

`=>` "Fat arrow" function expression.

`class` expression.

`let` expression.

`a + b` Addition operator.

`a - b` Subtraction operator.

`a * b` Multiplication operator.

`a / b` Division operator.

`a % b` Modulo operator.

`a++` Increment operator.

`a--` Decrement operator.

`a == b` Equality operator.

`a is b` Identity operator.

`a != b` Inquality operator.

`a > b` Greater than operator.

`a >= b` Greater than or equal operator.

`a < b` Less than operator.

`a <= b` Less than or equal operator.

`a && b` Logical AND operator.

`a || b` Logical OR operator.

`!a` Logical NOT operator.

`a & b` Binary AND operator.

`a | b` Binary OR operator.

`a ^ b` Binary XOR operator.

`a << b` Binary left shift operator.

`a >> b` Binary right shift operator.

`~a` Binary complement operator.

`a = b` Assignment operator.

`a <- b` Initialization assignment operator.

`a : b` JSON assignment operator.

`f(/* ... */)` Call operator.

`x.m(/* ... */)` Method call operator.

`a[b]` Read operator.

`a @f@ b` Binary function operator.

`@f a` Decorator.

`...a` Spread operator

`a ? b : c` Conditional (ternary) operator.

`start..stop` or `start..stop..step` Range operator.

`a instanceOf b` "Instance of" operator.

`delete a` Delete operator.

`await a` Await operator.

`a.b` Dot operator.