Selenium WebDriver JS - 显式等待

Question

I am using the selenium-webdriverjs. I want to wait for a certain element to be displayed for which I have created an explicit wait as follows and it works just fine,

var displayed = false;
driver.wait(function(){
    driver.findElement(locator).isDisplayed().then(function(value){
        displayed = value;
    });
    return displayed;
}, timeout);

Is this the best I can do or is there a better way to do this? The reason I ask is that the first time ever the wait callback is called (in my case) it will always return false. Only subsequently when the isDisplayed promise is executed will the value of displayed change.

Answer 1

Your code is mixing a synchronous return with asynchronous callbacks, the following code should do the right thing:

return driver.wait(function() {
    return driver.findElement(locator).isDisplayed();
}, timeout);

The inner function will return a promise that driver.wait will wait for and will take its value (true/false) as the waiting condition.

Answer 2

To avoid much of the confusion involved in the asynchronous flavors of webdriver and js, you could give webdriver-sync a try: https://npmjs.org/package/webdriver-sync

It's been my experience that the async versions of the webdriver API become difficult to read after too many nested callbacks.

This of course assumes that you don't have requirements to remain asynchronous.

Disclaimer: I am the creator of this piece of software (webdriver-sync)