Javascript Promise对象学习

 

ES6中的Promise对象

var p = new Promise(function(resolve, reject){
    window.setTimeout(function(){
        console.log("1",1);
        resolve(1);
    },10);
});
p.then(function(a){
    return new Promise(function(resolve,reject){
        window.setTimeout(function(){
            console.log("2",a+1);
            resolve(a + 1);
        },10);
    });
}).then(function(a){
    return new Promise(function(resolve,reject){
        window.setTimeout(function(){
            console.log("3",a+1);
            resolve(a + 1);
        },10);
    });
}).then((a)=>new Promise((resolve,reject)=>{
    window.setTimeout(function(){
        console.log("52222",a+1);
        resolve(a + 1);
    },10);
}));

　　

 

for循环中的ajax请求依次执行，而不是无序执行。

(function () {


    var ajax = function(callback){
        window.setTimeout(function(){
            callback(new Date());
        },1000);
    };

    var promiseAjax = function(num){
        return function (pre){
            return new Promise(function (resolve, reject) {
                ajax(function (d) {
                    console.log(num,d);
                    resolve(d);
                });
            });
        }
    } ;



    var p = promiseAjax(-1)();
    for (var i = 0; i < 10; i++) {
        p = p.then(promiseAjax(i));
    }


})();

　　

 

 

 

 

 

 

Angular中的$q对象

    var $q = {};
    var deferred = $q.defer();
    var promise = deferred.promise;
    promise.then(function(a){
        return a + "222"
    }).then(function(a){
        var deferred = $q.defer();
        window.setTimeout(function(){
            deferred.resolve("333");
        },100);
        return deferred.promise;
    });
    deferred.resolve("1111");

　　

var deferred = $q.defer()

...(and then from console inspection)...

$q: Object {defer: function, reject: function, when: function, all: function}

deferred: Object {resolve: function, reject: function, notify: function, promise: Object}

deferred.promise: Object {then: function, catch: function, finally: function}

 

$q.reject(reason) returns a rejected promise with the reason passed as argument and defered. Reject rejects an existent defered whether its process has finished or not.

　　

 

 

 

 

try、catch、throw和then、catch、reject