javascript - Protractor 函数返回未定义？

Question

这更多的是一个 JavaScript 问题，但它是尝试使用 Protractor 测试来实现的。

//fileA.js
element(by.id('page-element').getText().then(function() {
    var currentPremium = fileB.getSixMonthPremium(); // calls the function in fileB.js

    element(by.id('page-element').getText().then(function() {
        console.log(currentPremium); // prints undefined
        fileB.compareValue(currentPremium, ..., ...,);
    });
});


//fileB.js
this.getSixMonthPremium() = function() {
    element(by.id('full-premium').isDisplayed().then(function(displayed) {
        if (displayed) {
            element(by.id('full-premium').getText().then(function(currentPremium) {
                console.log('Current Premium - ' + currentPremium); // prints string of $XXX.xx
                return currentPremium; //seems to be returning undefined?
            });
        }
    });
});

当变量currentPremium从函数调用返回后尝试使用它时，它总是未定义的。我究竟做错了什么？

Answer 1

欢迎使用 Javascript 异步调用!

您需要从 getSixMonthPremium() 调用返回一个 Promise，然后在该调用返回后继续工作。

this.getSixMonthPremium() = function() {
    return new Promise(function(resolve,reject){
        element(by.id('full-premium').isDisplayed().then(function(displayed) {
            if (displayed) {
                element(by.id('full-premium').getText().then(function(currentPremium) {
                    console.log('Current Premium - ' + currentPremium); // prints string of $XXX.xx
                    resolve(currentPremium); //seems to be returning undefined?
                });
            }
        });
    })
});

然后你将通过执行以下操作来处理该 promise :

fileB.getSixMonthPremium().then(function(premium){
    ...handle premium
});