javascript - 未捕获的类型错误 : undefined is not a function

Question

下面的 JavaScript 代码片段在 .done 语句上出现错误。错误是“未捕获的类型错误:未定义不是函数”既然我们可以使用 did 和 Promise 知道为什么会出现这个错误吗？

var promise = new Promise(function(resolve,reject)
                {

                    if(true)
                    {
                        console.log("1");

                    }
                    else
                        console.log("2");


                });
    promise.then( function(data1) {

                     if(true)
                    {
                        console.log("3");
                    }

                    else
                       console.log("4");
                })
                .then( function(data2) {

                     if(true)
                    {
                        console.log("5");
                    }
                    else
                        console.log("6");

                })
               .done( 
                    function(response) {
                       console.log("done")
                    });
                .fail(
                    function() {
                        console.log("fail");
                    });

Answer 1

Promise API 中没有 done 和 fail 这样的方法，只有 then 和 catch 在对象级别:https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise#Methods

Promise.prototype.then(onFulfilled, onRejected)

Appends fulfillment and rejection handlers to the promise, and returns a new promise resolving to the return value of the called handler.

Promise.prototype.catch(onRejected)

Appends a rejection handler callback to the promise, and returns a new promise resolving to the return value of the callback if it iscalled, or to its original fulfillment value if the promise is insteadfulfilled.