Promise.js with AJAX

使用

        Promise.timeout(f1(), 2000).then(f2, function () {

            alert("timeout");

        }).wait(5000).then(f3);

        function f1() {

            var promise = Promise();

            setTimeout(function () {

                console.log(1);

                promise.resolve("from f1");

            }, 1500)

            return promise;

        }

        function f2() {

            var promise = Promise();

            setTimeout(function () {

                console.log(2);

                promise.resolve();

            }, 1500)

            return promise;

        }

        function f3() {

            var promise = Promise();

            setTimeout(function () {

                console.log(3);

                promise.resolve();

            }, 1500)

            return promise;

        }

AJAX

function xhr(options) {

    var promise = Promise(),

        req = new XMLHttpRequest();

    req.open(options.method || 'GET', options.url, true);

    // Set request headers if provided.

    Object.keys(options.headers || {}).forEach(function (key) {

        req.setRequestHeader(key, options.headers[key]);

    });

    req.onreadystatechange = function (e) {

        if (req.readyState !== 4) {

            return;

        }

        if ([200, 304].indexOf(req.status) === -1) {

            promise.reject('Server responded with a status of ' + req.status);

        } else {

            promise.resolve(e.target.result);

        }

    };

    req.send(options.data || void 0);

    return promise;

}

使用：

xhr({ url: "xxx.php?a=xxx" }).then(function (msg) {

})

当然，promise支持等待N个AJAX都完成之后进行回掉:

Promise(xhr({ url: "a.php?c=xxx" }), xhr({ url: "b.php?d=xxx" })).then(function () {

})

上面的写法的Promise.when的缺省形式。

Promise.timeout with AJAX

这里需要思考的是:timeout是属于AJAX还是属于Promise?

如果属于AJAX,那么就有下面这种形式：

xxx.ajax("xxx.php", {

    method: "GET",

    data: null,

    onSuccess: function () { },

    onTimeout: function () { },

    timeout: 30000

});

如果属于Promise:

Promise.timeout(xhr({ url: "xxx.php" }), 30000).then(

    function () { },

    function () { }

)