使用promis串行化异步操作

function async1() {
var defer = Promise.defer()
setTimeout(function(){
defer.resolve('async1')
}, 1300);
return defer.promise;
}

function async2(param) {
var defer = Promise.defer()
setTimeout(function(){
defer.resolve( param + 'async2')
}, 1100);
return defer.promise;
}

async1()
.then(function(d){
return async2(d);
})
.then(function(d){
console.log(d); //输出async1async2
});