Why is JavaScript not sufficient itself?

Basic Types

• Boolean
• Number
• String
• Array
• Object
• Undefined

• Enum
• Tuple
• Any
• Void
• Never

Interfaces - Optional Properties

interface SquareConfig {
    color?: string;
    width?: number;
}

function createSquare(config: SquareConfig) {
    // ...
}

let mySquare = createSquare({color: "black", widht: 50});
                

Compile time error:

test.ts(17,47): error TS2345: Argument of type
'{ color: string; widht: number; }'
is not assignable to parameter of type 'SquareConfig'.
Object literal may only specify known properties,
and 'widht' does not exist in type 'SquareConfig'.
                

Thanks

www.typescriptlang.org