TypeScript call function with Rest Parameters from another with Rest Parameters

Question

In TypeScript it is possible to declare a function with "Rest Parameters":

function test1(p1: string, ...p2: string[]) {
    // Do something
}

Suppose that I declared another function that called test1:

function test2(p1: string, ...p2: string[]) {
    test1(p1, p2);  // Does not compile
}

The compiler produces this message:

Supplied parameters do not match any signature of call target: Could not apply type 'string' to argument 2 which is of type 'string[]'.

How can test2 call test1 will the supplied arguments?

Answer 1

Try the Spread Operator. It should allow for the same effect as in Jeffery's answer but has a more concise syntax.

function test2(p1: string, ...p2: string[]) {
    test1(...arguments);
}

Answer 2

There's no way to pass p1 and p2 to test1 from test2. But you could do this:

function test2(p1: string, ...p2: string[]): void {
    test1.apply(this, arguments);
}

That's making using of Function.prototype.apply and the arguments object.

If you don't like the arguments object or you don't want all the arguments passed in exactly the same order you can do something like this:

function test2(p1: string, ...p2: string[]) {
    test1.apply(this, [p1].concat(p2));
}

Answer 3

Yes, it doesn't compile as you are doing wrong thing. Here is the right way:

function test1(p1: string, ...p2: string[]) {
    // Do something
}

function test2(p1: string, ...p2: string[]) {
    test1(p1, ...p2);
}