我想创建一个返回 promise 的函数,如果其中出现错误,它会返回 promise reject。
function promiseFunc(options) {
return new Promise(() => {
return options;
});
}
function myfunc(options) {
return new Promise(() => {
if (!options) throw new Error("missing options");
return promiseFunc(options).then((result) => {
if (result.throwerr) throw new Error("thrown on purpose");
return result.value;
});
});
};
我的测试如下:
const myfunc = require("./myfunc");
describe('myfunc', () => {
it('should fail without options', () => {
return myfunc()
.then((result) => { throw new Error(result) }, (err) => {
console.log("test #1 result:", err.message === "missing options");
});
});
it('should fail on options.throwerr', () => {
return myfunc({throwerr: true})
.then((result) => {}, (err) => {
console.log("test #2 result:", err.message === "thrown on purpose");
});
});
it('should return options.value', () => {
return myfunc({value: "some result", throwerr: false})
.then((result) => {
console.log("test #3 result:", result === "some result");
}, (err) => {});
});
});
第一次测试通过,但第二次和第三次失败。
Log #2 甚至没有运行,所以我假设“故意抛出”搞砸了一些东西,因此我创建了测试 #3,我没有抛出任何东西,但它仍然失败。 我错过了什么?
解决方法:
function promiseFunc(options) {
return new Promise(resolve => {
return resolve(options);
});
}
function myfunc(options) {
return new Promise((resolve, reject) => {
if (!options) throw new Error("missing options");
return promiseFunc(options).then(result => {
if (result.throwerr) throw new Error("thrown on purpose");
return resolve(result.value);
}).catch(err => {
return reject(err);
});
});
};
最佳答案
您忘记传递一个带有 resolve 和 reject 参数的函数,所以您的 promise 不起作用。
function promiseFunc(options) {
return new Promise(resolve => { // resolve function
resolve(options)
})
}
module.exports = function myfunc(options) {
return new Promise((resolve, reject) => { // since you may either resolve your promise or reject it, you need two params
if (!options) {
return reject(new Error("missing options"))
}
return promiseFunc(options).then(result => {
if (result.throwerr) {
return reject(new Error("thrown on purpose"))
}
resolve(result.value)
})
})
}
...和测试(mocha)
const assert = require('assert'),
myfunc = require("./myfunc")
describe('myfunc', () => {
it('should fail without options', done => { // mind the callback, promises are always async
myfunc()
.catch(err => {
assert(err.message === "missing options")
done() // <- called here
})
})
it('should fail on options.throwerr', done => {
myfunc({throwerr: true})
.catch(err => {
assert(err.message === "thrown on purpose")
done()
})
})
it('should return options.value', done => {
return myfunc({value: "some result", throwerr: false})
.then(result => {
assert(result === "some result")
done()
})
})
})
关于javascript - 使用 promise ,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/36652195/