Promise をつなげる

直列

Promise.resolve().then(function(){

        return new Promise(function(resolve, reject){

            resolve()

        })

}).then(function(){

        return new Promise(function(resolve, reject){

            resolve()

        })

}).then(function(){

        return new Promise(function(resolve, reject){

            resolve()

        })

})

並列

const promiseArray = [];

const initializeInit = new Promise((resolve, reject) => {

        resolve();

})

promiseArray.push(initializeInit);

const initializeStyle = new Promise((resolve, reject) => {

        resolve();

})

promiseArray.push(initializeStyle);

return new Promise((resolve, reject) => {

        Promise.all(promiseArray).then(() => {

            resolve();

        })

})

(参考記事)