JavaScript:4个asyncronys函数在继续之前依次等待对方完成？

Question

// NOTE: localDataStore is a function to stringify/parse an item from localStorage

function removeCookie() {
chrome.cookies.remove({"name":"v1guid","url":"http://website.com"},function (cookie){
    console.log("cookie removed");
});
}

function getCookie() {
chrome.cookies.get({"url": "http://website.com", "name": "v1guid"}, function(cookie) {
    console.log(cookie);
    if(cookie !== null) {
        console.log("getting cookie");
        localDataStore.set("cookie", cookie);
        console.log(localDataStore.get("cookie"));
    }
});
}

function setCookie() {
var cookiedata = localDataStore.get("cookie");
chrome.cookies.set({
    "url": "http://website.com", 
    "name": cookiedata.name, 
    "value": cookiedata.value,
    "domain": cookiedata.domain,
    "path": cookiedata.path,
    "secure": cookiedata.secure,
    "httpOnly": cookiedata.httpOnly,
    "storeId": cookiedata.storeId}, function(cookie) {
    console.log("cookietest");
    console.log(JSON.stringify(cookie));
});
}

function minePosts() {
// Do a bunch of stuff
}

getCookie();
removeCookie();
minePosts();
setCookie();

Answer 1

可以使用回调或$.deferred（）来推迟函数。前者更简单，而后者更健壮，因为您可以使用deferred.reject()来处理错误状态。

1）回调

function removeCookie(callback) {
    chrome.cookies.remove({"name":"v1guid","url":"http://website.com"},function (cookie){
        console.log("cookie removed");
        callback();
    });
}

等等。

getCookie(function(){
    removeCookie(function(){
        minePosts(function(){
            setCookie(function(){
                // do something
            });
        });
    });
});

function removeCookie() {
    var deferred = $.Deferred();
    chrome.cookies.remove({"name":"v1guid","url":"http://website.com"},function (cookie){
        console.log("cookie removed");
        deferred.resolve();
    });
    return deferred.promise();
}

getCookie().then(function(){
    removeCookie().then(function(){
        minePosts().then(function(){
            setCookie().then(function(){
                // do something
            });
        });
    });
});

getCookie()
    .then(removeCookie)
    .then(minePosts)
    .then(setCookie)
    .then(function(){
        // do something
    });