程式碼片段1

var prepayment_apply,prepayment_operational; // loadMain().then(loadBtn()).then(function () { console.log(prepayment_operational); // undefined return loadProgress(); }); // fun1 function loadMain() { return $.ajax({ url:'...', success:function (data) { prepayment_apply = data.prepayment_apply; } }) } // fun2 function loadBtn() { return $.ajax({ url:'...', success:function (data) { prepayment_operational = data.prepayment_operational; } }) } // fun3 $.ajax({ url:'...', type:'get', dataType:'json', load_animation:true, success:function (data) { ... } })

我將$.ajax封裝到函數函數中時，用promise寫法打出的prepayment_operational是undefined。

程式碼片段2

var prepayment_apply,prepayment_operational; // loadMain().then(function () { $.ajax({ url: '...', success: function (data) { prepayment_operational = data.prepayment_operational; } }) } ) .then(function () { console.log(prepayment_operational); // '111' return loadProgress(); });

當我直接把ajax寫在then就能得到我想要的值。並且當我把程式碼段1中的

loadMain().then(loadBtn()).then(function () { console.log(prepayment_operational); // undefined return loadProgress(); });

改成

loadMain().then(function () {return loadBtn()}).then(function () { console.log(prepayment_operational); // undefined return loadProgress(); });

程式碼段1也能正常console出prepayment_operational。
想請教下這是為什麼。