Summary of how angularjs handles multiple asynchronous requests

In actual business, it is often necessary to wait for several requests to be completed before proceeding to the next step. But $http in angularjs does not support synchronous requests.

Solution one:

$http.get('url1').success(function (d1) {
        $http.get('url2').success(function (d2) {
            //处理逻辑
        });
    });

Solution two:

The methods in then will be executed in order.

var app = angular.module('app',[]);
app.controller('promiseControl',function($scope,$q,$http) {
    function getJson(url){
        var deferred = $q.defer();
        $http.get(url)
            .success(function(d){
                d = parseInt(d);
                console.log(d);
                deferred.resolve(d);
            });
        return deferred.promise;
    }
    getJson('json1.txt').then(function(){
        return getJson('json2.txt');
    }).then(function(){
        return getJson('json1.txt');
    }).then(function(){
        return getJson('json2.txt');
    }).then(function(d){
        console.log('end');
    });
});

Solution 3:

The first parameter of the $q.all method can be an array (object). After the contents in the first parameter are executed, the method in then will be executed. All return values ​​of the first parameter method will be passed in in the form of arrays (objects).

var app = angular.module('app',[]);
app.controller('promiseControl',function($scope,$q,$http) {
    $q.all({first: $http.get('json1.txt'),second: $http.get('json2.txt')}).then(function(arr){
        console.log(arr);
        angular.forEach(arr,function(d){
            console.log(d);
            console.log(d.data);
        })
    });
});

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