How to pass a function in Puppeteers .evaluate() method?

Question

Whenever I try to pass a function, like this:

var myFunc = function() { console.log(\"lol\"); };

await page.evaluate(func => {
 func();
 return true;
},          


        

Answer 1

Created a helper function that wraps page.evaluate:

const evaluate = (page, ...params) => browserFn => {
    const fnIndexes = [];
    params = params.map((param, i) => {
        if (typeof param === "function") {
            fnIndexes.push(i);
            return param.toString();
        }
        return param;
    });
    return page.evaluate(
        (fnIndexes, browserFnStr, ...params) => {
            for (let i = 0; i < fnIndexes.length; i++) {
                params[fnIndexes[i]] = new Function(
                    " return (" + params[fnIndexes[i]] + ").apply(null, arguments)"
                );
            }
            browserFn = new Function(
                " return (" + browserFnStr + ").apply(null, arguments)"
            );
            return browserFn(...params);
        },
        fnIndexes,
        browserFn.toString(),
        ...params
    );
};

export default evaluate;

Takes all parameters and converts functions to string.
Then recreates functions in browser context.
See https://github.com/puppeteer/puppeteer/issues/1474

You can use this function like so:

const featuredItems = await evaluate(page, _getTile, selector)((get, s) => {
    const items = Array.from(document.querySelectorAll(s));
    return items.map(node => get(node));
});