I stumble upon this code snippet while working on fastify.
module.exports = async function (fastify, opts) {
fastify.register(proxy, {
upstream: 'https://news.ycombinator.com/',
async preHandler(request, reply) {
if (request.query.token !== 'abc') {
throw fastify.httpErrors.unauthorized();
}
},
});
};
Looks like it calls fastify.register with two parameters and the second parameter is an object. The first field is upstream but I don't get what comes next. What is this syntax after async preHandler(request, reply)...?
fastify.register seemingly has this signature: fastify.register(proxy, {});. So the second parameter is an object.
As stated in MDN and by Andreas in comments you can have an object that contains a method signature. So your object can be declared as:
{
upstream: string,
preHandler(request, reply){}
}
Where preHandler(request, reply){} is essentially a shorthand for preHandler: function(request, reply){}
You can then declare this method signature async (again as stated in docs). Which results in:
{
async preHandler(request, reply){}
}
The above could also be declared as:
{
preHandler: async function(request, reply){}
}