The values returned from evaluate function should be json serializeable.
https://github.com/GoogleChrome/puppeteer/issues/303#issuecomment-322919968
the solution is to extract the href values from the elements and return it.
await this.page.evaluate((sel) => {
let elements = Array.from(document.querySelectorAll(sel));
let links = elements.map(element => {
return element.href
})
return links;
}, sel);