all.js

/*  Using Promise.all to execute multiple async functions simultaneously */
Promise.all([runEvalScript('firstTask()'), runEvalScript('secondTask()'), runEvalScript('thirdTask()')])
    .then(function(result) {
        //result is an array of values resulted from the three fulfilled promises.
    })
    .catch(function(error) {
        //Triggers if at least one of the promises were rejected.
    });