async function

async function (param0) {
  statements
}
async function (param0, param1) {
  statements
}
async function (param0, param1, /*  ,*/ paramN) {
  statements
}

async function name(param0) {
  statements
}
async function name(param0, param1) {
  statements
}
async function name(param0, param1, /*  ,*/ paramN) {
  statements
}

function resolveAfter2Seconds(x) {
  return new Promise((resolve) => {
    setTimeout(() => {
      resolve(x);
    }, 2000);
  });
}

// 
const add = async function (x) {
  const a = await resolveAfter2Seconds(20);
  const b = await resolveAfter2Seconds(30);
  return x + a + b;
};

add(10).then((v) => {
  console.log(v); // 4  60
});

//  IIFE 
(async function (x) {
  const p1 = resolveAfter2Seconds(20);
  const p2 = resolveAfter2Seconds(30);
  return x + (await p1) + (await p2);
})(10).then((v) => {
  console.log(v); // 2  60
});