Question

我正在尝试通过回调调用map函数。但是我无法通过以下错误消息调用回调函数。

> tsc && node index.js

(node:17460) UnhandledPromiseRejectionWarning: Error: Evaluation failed: ReferenceError: translateText is not defined
    at mapFunc (__puppeteer_evaluation_script__:3:13)
    at Array.map (<anonymous>)
    at __puppeteer_evaluation_script__:13:22
    at ExecutionContext.evaluateHandle (C:\github\dojo-tools\node_modules\puppeteer\lib\ExecutionContext.js:121:13)
    at process._tickCallback (internal/process/next_tick.js:68:7)
  -- ASYNC --
    at ExecutionContext.<anonymous> (C:\github\dojo-tools\node_modules\puppeteer\lib\helper.js:110:27)
    at ExecutionContext.evaluate (C:\github\dojo-tools\node_modules\puppeteer\lib\ExecutionContext.js:48:31)
    at ExecutionContext.<anonymous> (C:\github\dojo-tools\node_modules\puppeteer\lib\helper.js:111:23)
    at ElementHandle.$$eval (C:\github\dojo-tools\node_modules\puppeteer\lib\JSHandle.js:453:50)
    at process._tickCallback (internal/process/next_tick.js:68:7)
  -- ASYNC --
    at ElementHandle.<anonymous> (C:\github\dojo-tools\node_modules\puppeteer\lib\helper.js:110:27)
    at getHTML (C:\github\dojo-tools\index.js:77:32)
    at process._tickCallback (internal/process/next_tick.js:68:7)
(node:17460) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 1)
(node:17460) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

我想在回调函数中调用外部函数。因为我想处理每个数组项。

下面是我当前的代码。

function translateText() {...}

async function getHTML() {
    const browser = await puppeteer.launch({
        headless: false
    });

    const func = (nodes: Array<Element>) => {
        const mapFunc = (n: Element) => {
            translateText(n.textContent || "NO STRING"); // <-------- ERROR
            switch (n.tagName) {
                case 'P':
                    return `  * ${n.textContent}`;
                case 'LI':
                    return `    * ${n.textContent}`;
                default:
                    return `    * COULDNOT ANALYZE - ${n.textContent}`;
            }
        }
        return nodes.map(mapFunc);
    }

    const page = await browser.newPage();
    await page.goto('https://azure.microsoft.com/en-us/updates/the-azure-us-gov-iowa-region-is-being-retired-april-30-2020/'); // 表示したいURL
    const elm = await page.$('#main > div > div:nth-child(3) > div > div:nth-child(1)');
    if (elm !== null) {
        const data = await elm.$$eval('p, li', func);
        console.log(data);
    }
    browser.close();
}

能否让我知道如何在地图回调函数中访问外部函数？

Answer 1

看起来像elm.$$eval('p, li', func)在浏览器上下文中评估func。因此，没有简单的方法可以调用外部函数。简单的解决方案是使translateText的{{1}}内部功能。

如何在匿名和回调函数中调用外部函数

1 个答案: