RuntypeScript

Comments

// Only single line comments

Declarations

var x = y;
var x: T = y;
const x = y;
const x: T = y;

Declaration with no declared type:

const x = y;

is a shorthand for:

const x: ~y = y;

except that y is evaluated only once.

Declaration cannot shadow other variables.

Assignment

Left-hand side of an assignment can only consist of an identifier followed by an optional chain of indexing expressions. Indexes themselves can be arbitrary expressions.

An assignment results in a runtime error if a variable after assignment (including mutation) is not assignable to its declared type.

const x: { prop: string } = { prop: "foo" };

// allowed
x["prop"] = "bar";

// not allowed, { prop: 1 } not assignable to { prop: string }
x["prop"] = 1;

You can also use the following assignment shorthands:

• +=
• -=
• *=
• /=
• %=
• |=
• &=

If, elif, else

if (CONDITION) {
    // (...)
} elif (CONDITION) {
    // (...)
} else {
    // (...)
}

Braces are always required.

While

while (CONDITION) {
    // (...)
}

Braces are always required.

You can use break and continue statements inside a while loop.

Return

return EXPRESSION;
return; // shorthand for return nil;