Tips for waiting for an HTML element to load in a Selenium JavaScript testing script

Question

Tips for waiting for an HTML element to load in a Selenium JavaScript testing script

I'm struggling to find a way to wait for an element to load in a javascript selenium test script. The closest thing I've come across is until.elementLocated, but it seems to throw an immediate exception.

Is there a method to delay throwing the "NoSuchElementError" exception until the timeout has expired?

"NoSuchElementError: no such element: Unable to locate element: {"method":"xpath","selector":"//button[text()='NEXT']"}"

Or is there any way to avoid this exception altogether when waiting for an element in Selenium?

  await driver.wait(function () {
        let text = "//button[text()='" + "NEXT" + "']";
        let button = By.xpath(text);
        return until.elementLocated(button);
    }, 40000).then(() => {console.log("element is located")})

javascript selenium-webdriver

Answer 1

Answer №1

My primary focus is on utilizing Selenium with Java or Python, while I also delve into JS using Puppeteer or Playwright. As a result, I have not yet tested the initial solution (although I am confident it would be effective).

Based on the documentation, driver.wait requires a function and waits for its condition to become true. Therefore, you can utilize findElements which does not generate exceptions and wait for the length of the returned collection to exceed 0.

const getElements = (locator) => driver.findElements(locator).then(els => els.length);
await driver.wait(() => getElements(By.xpath("//button[text()='NEXT']")), 10000);

If needed, you can create your own custom waiter that will wait for a condition to be true and return an element. While this approach may not be as clean, it is adaptable across different frameworks.

const waitFor = async (action, timeoutMs, pollIntervalMs) => {
  let isTimeout = false;
  const timeoutId = setTimeout(() => {
    isTimeout = true;
  }, timeoutMs);
  let result;
  while (!isTimeout && !result) {
    result = await action();
    await new Promise(resolve => setTimeout(resolve, pollIntervalMs));
  }

  clearTimeout(timeoutId);
  if (isTimeout) {
    throw new Error('Timeout exceeded!');
  } else {
    return result;
  }
};

const getElementOrNull = (locator) => driver.findElements(locator).then(els => els.length ? els[0] : null);

const element = await waitFor(() => getElementOrNull(By.xpath("//button[text()='NEXT']")), 10000, 500);

Answer 2

My primary focus is on utilizing Selenium with Java or Python, while I also delve into JS using Puppeteer or Playwright. As a result, I have not yet tested the initial solution (although I am confident it would be effective).

Based on the documentation, driver.wait requires a function and waits for its condition to become true. Therefore, you can utilize findElements which does not generate exceptions and wait for the length of the returned collection to exceed 0.

const getElements = (locator) => driver.findElements(locator).then(els => els.length);
await driver.wait(() => getElements(By.xpath("//button[text()='NEXT']")), 10000);

If needed, you can create your own custom waiter that will wait for a condition to be true and return an element. While this approach may not be as clean, it is adaptable across different frameworks.

const waitFor = async (action, timeoutMs, pollIntervalMs) => {
  let isTimeout = false;
  const timeoutId = setTimeout(() => {
    isTimeout = true;
  }, timeoutMs);
  let result;
  while (!isTimeout && !result) {
    result = await action();
    await new Promise(resolve => setTimeout(resolve, pollIntervalMs));
  }

  clearTimeout(timeoutId);
  if (isTimeout) {
    throw new Error('Timeout exceeded!');
  } else {
    return result;
  }
};

const getElementOrNull = (locator) => driver.findElements(locator).then(els => els.length ? els[0] : null);

const element = await waitFor(() => getElementOrNull(By.xpath("//button[text()='NEXT']")), 10000, 500);

Tips for waiting for an HTML element to load in a Selenium JavaScript testing script

Answer №1

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