ajaxでの同期と非同期の違いと使用シーンを深く理解する

3607 ワード

Ajax javascript

まず2つのコードを行って、この2つのコードのconsoleを当てます.logの実行順序と結果:
コード1:

                    $.ajax({
                        type: "post",
                        async:true, //           true
                        url: "/teacher/ajaxtimeline",
                        data: {"month": month, "uid":uid);?>},
                        dataType: "json",
                        success: function(data) {
                            //  data.canNotSetDays       [9,10,11]
                            $.each(data.canNotSetDays, function(i, item) {
                                canNotSetDays.push(item);
                            });

                            console.log('**********ajax result ************');
                            //       canNotSetDays   ，            9
                            console.log(canNotSetDays);
                            console.log(canNotSetDays.length);
                            console.log(canNotSetDays.indexOf(9));

                        }
                    });

                    console.log('***********after ajax ***********');

                    //       canNotSetDays   ，   0，            9
                    console.log(canNotSetDays);
                    console.log(canNotSetDays.length);
                    console.log(canNotSetDays.indexOf(9));

                    console.log('**********delay two seconds************');

                    setTimeout(function(){
                        //  2        canNotSetDays   ，            9
                        console.log(canNotSetDays);
                        console.log(canNotSetDays.length);
                        console.log(canNotSetDays.indexOf(9));
                    }, 2000);

コード2:

                     $.ajax({
                        type: "post",
                        async:false, //           true
                        url: "/teacher/ajaxtimeline",
                        data: {"month": month, "uid":uid);?>},
                        dataType: "json",
                        success: function(data) {
                            //  data.canNotSetDays       [9,10,11]
                            $.each(data.canNotSetDays, function(i, item) {
                                canNotSetDays.push(item);
                            });

                            console.log('**********ajax result ************');
                            //       canNotSetDays   ，            9
                            console.log(canNotSetDays);
                            console.log(canNotSetDays.length);
                            console.log(canNotSetDays.indexOf(9));

                        }
                    });

                    console.log('***********after ajax ***********');

                    //       canNotSetDays   ，            9
                    console.log(canNotSetDays);
                    console.log(canNotSetDays.length);
                    console.log(canNotSetDays.indexOf(9));

                    console.log('**********delay two seconds************');

                    setTimeout(function(){
                        //  2          canNotSetDays   ，            9
                        console.log(canNotSetDays);
                        console.log(canNotSetDays.length);
                        console.log(canNotSetDays.indexOf(9));
                    }, 2000);

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