【JavaScript】Callback和Promise

參考教學https://www.youtube.com/watch?v=UGf0fGMxDgE&index=22&list=UUr7GjHXlkad7hMcXMc-R3ag

callback寫法

 function typo(word, callback) {
            setTimeout(function () {
                console.log(word)
                callback()
            }, Math.random() * 100);
        }

        function logall() {

            typo(1, function () {
                typo(2, function () {
                    typo(3)
                })
            });

        }

        logall()
        console.log(4)

Promise寫法

function typo(word) {
            return new Promise(function (res, rej) {
                setTimeout(function () {
                    console.log(word)
                    res()
                }, Math.random() * 100);
            })

        }

        function logall() {
            typo(1).then(function () {
                return typo(2)
            }).then(function () {
                return typo(3)
            })

        }

        logall()
        console.log(4)

​