Transpilation

Given a class SomeClass, let’s see how the TypeScript is transpiled into JavaScript.

TypeScript source

class SomeClass {

    public static SomeStaticValue: string = "hello";
    public someMemberValue: number = 15;
    private somePrivateValue: boolean = false;

    constructor () {
        SomeClass.SomeStaticValue = SomeClass.getGoodbye();
        this.someMemberValue = this.getFortyTwo();
        this.somePrivateValue = this.getTrue();
    }

    public static getGoodbye(): string {
        return "goodbye!";
    }

    public getFortyTwo(): number {
        return 42;
    }

    private getTrue(): boolean {
        return true;
    }

}

JavaScript source

When transpiled using TypeScript v2.2.2, the output is like so:

var SomeClass = (function () {
    function SomeClass() {
        this.someMemberValue = 15;
        this.somePrivateValue = false;
        SomeClass.SomeStaticValue = SomeClass.getGoodbye();
        this.someMemberValue = this.getFortyTwo();
        this.somePrivateValue = this.getTrue();
    }
    SomeClass.getGoodbye = function () {
        return "goodbye!";
    };
    SomeClass.prototype.getFortyTwo = function () {
        return 42;
    };
    SomeClass.prototype.getTrue = function () {
        return true;
    };
    return SomeClass;
}());
SomeClass.SomeStaticValue = "hello";

Observations

The modification of the class’ prototype is wrapped inside an IIFE.
Member variables are defined inside the main class function.
Static properties are added directly to the class object, whereas instance properties are added to the prototype.

Found a mistake? Have a question or improvement idea? Let me know.

Table Of Contents