how to wait for a function to finish code example

Example: how to wait for a function to finish in javascript

function doFirst() {
  return new Promise(function(resolve, reject) {
    //do a thing
      if (){
          return reject(value);
  	  }
      resolve(value);
    });
  });
}

async function doSecond() {
    var outputValue = await doFirst();
    console.log(outputValue);
}