spark for typescript syntax

Question

I try to use Spark with TypeScript but when I write this

Spark.get("/facture", (req, res) => { 
    chalk.red('Hello test');
    chalk.green('Hello word');
})

It return me undefined but when I write only 1 line it works

Spark.get("/facture", (req, res) => 
    chalk.green('Hello word');
)

I think that the problem come from the syntax. Someone can help me please

Answer 1

When using arrow functions, if they are one liners you can omit the { } and the value returned by the expression will be the return value of the function.

In essence:

Spark.get("/facture", (req, res) => 
    chalk.green('Hello word');
)

Transpiles to:

Spark.get("/facture", function (req, res) {
    return chalk.green('Hello word');
});

However when you have more than one statement and you make a body for the arrow function you must manually return the value as you would in normal functions.

You can easily see it when transpiled.

Spark.get("/facture", (req, res) => { 
    chalk.red('Hello test');
    chalk.green('Hello word');
})

Transpiles to:

Spark.get("/facture", function (req, res) {
    chalk.red('Hello test');
    chalk.green('Hello word');
});

If you want to return something you have to write the return statement:

Spark.get("/facture", (req, res) => { 
    chalk.red('Hello test');
    return chalk.green('Hello word');
})

So it ends up like this in javascript:

Spark.get("/facture", function (req, res) {
    chalk.red('Hello test');
    return chalk.green('Hello word');
});

You can see the examples in the playground here and learn more about arrow functions on the MDN page for them here.