CODEWITHSUNDEEP
node.js
OneTwo
OneTwo

Reputation: 2483

How to check if the result of a nodejs function?

I'm completely new to nodejs.

So I'm using puppeteer to call a webpage, I want to check if Jupyter exists on the webpage.

await page.evaluate((sel) => {
    if (typeof Jupyter == 'undefined') {
        jupyterundefined = true;
        return;
    } else {
        Jupyter.notebook.clear_all_output();
    }
}, 'dummy');

await page.waitFor(60000);
if(jupyterundefined){
   //do something else

It seems that the await function doesn't change the jupyterundefined variable, because it's asyn. But how can I check if it returns with the return I have there?

Upvotes: 1

Views: 30

Answers (1)

Orelsanpls
Orelsanpls

Reputation: 23515

The function page.evaluate(pageFunction[, ...args]) is returning a Promise that can hold a value, I would advise you to use it.

Like : 

const isJupyterUndefined = await page.evaluate((sel) => {
    // === void 0 is the same as typeof undefined
    if (Jupyter === void 0) {
        return true;
    }

    Jupyter.notebook.clear_all_output();

    return false;
}, 'dummy');

await page.waitFor(60000);

if (isJupyterUndefined){
   //do something else

Upvotes: 2

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