javascript - 使用 Mocha 测试 Promise 时出错 - 'TypeError: Cannot read property ' resolve'of undefined'

Question

我不断收到错误“TypeError:无法读取未定义的属性‘resolve’”，我不知道为什么会这样。有什么想法吗？

describe('render fn', () => {
    it('should return a string', () => {
        let filename = __filename, 
            content = 'Hello, World', 
            theme = './test.less';
        return file.render(filename, content, theme)
            .then((css) => {
                expect(css).to.be.a('string');
        });
    });
});

这是我要测试的代码:

render(filename, content, theme) {
    return new Promise((resolve, reject) => {
        let options = JSON.parse(JSON.stringify(this.config.renderOptions));

        if (theme)
            options.paths.push(path.resolve(this.config.theme.path, theme));

        options.paths.push(path.resolve(this.config[filename].resolve.root));

        less.render(content, options, (e, output) => {
            if (e != null) reject(e);
            resolve(output.css);
        });
    });
}

我已经为此工作了很长时间，如果有任何帮助，我将不胜感激。 谢谢!

Answer 1

I keep getting the error 'TypeError: Cannot read property 'resolve' of undefined,' and I don't know why it's happening. Any thoughts?

问题出在这一行:

options.paths.push(path.resolve(this.config[filename].resolve.root));

您尝试读取对象 this.config[filename] 上的属性 .resolve 的位置。错误消息告诉您该对象是 undefined。您的代码等于:

var myObject = undefined;
console.log(myObject.resolve); //Cannot read property 'resolve' of undefined

我无法从您在问题中列出的代码中判断出为什么 this.config[filename] 是 undefined。