In protractor, browser.isElementPresent vs element.isPresent vs element.isElementPresent

Question

In protractor, there are, basically, 3 ways to check if an element is present:

var elm = element(by.id("myid"));

browser.isElementPresent(elm);
elm.isPresent();
elm.isElementPresent();

Are these options equivalent and interchangeable, and which one should be generally preferred?

Solution 1

All function in a similar way with subtle differences. Here are few differences that i found -

elm.isPresent() -

1. Is an extension of ElementFinder and so waits for Angular to settle on page before executing any action.
2. It works when elm is an element(locator) or ElementFinder and not ElementArrayFinder. If multiple elements are returned using the locator specified then first element is checked if it isEnabled() in the DOM. Doesn't take any parameter as input.
3. Works best with Angular pages and Angular elements.
4. First preference to use whenever there is a need to find if an element is present.

elm.isElementPresent(subLoc) - (When there is a sub locator to elm)

1. Is an extension of ElementFinder and so waits for Angular to settle on page before executing any action.
2. Used to check the presence of elements that are sub elements of a parent. It takes a sub locator to the parent elm as a parameter. (only difference between this and the elm.isPresent())
3. Works best with Angular pages and Angular elements.
4. First preference to use whenever there is a need to check if a sub element of a parent is present.

browser.isElementPresent(element || Locator) -

1. Is an implementation of webdriver and so doesn't wait for angular to settle.
2. Takes a locator or an element as a parameter and uses the first result if multiple elements are located using the same locator.
3. Best used with Non-Angular pages.
4. First preference to use when testing on non-angular pages.

All of the above checks for the presence of an element in DOM and return a boolean result. Though angular and non-angular features doesn't affect the usage of these methods, but there's an added advantage when the method waits for angular to settle by default and helps avoid errors in case of angular like element not found or state element reference exceptions, etc...

Solution 2

I can't speak to which one is preferred but I was able to find the source code and examine it.

According to the docs, elm.isPresent() and elm.isElementPresent() are equivalent. Hope that helps.

Protractor API Docs

There is a link to View code just to the right of the title.

browser.isElementPresent(elm);

https://angular.github.io/protractor/#/api?view=webdriver.WebElement.prototype.isElementPresent

/**
 * Schedules a command to test if there is at least one descendant of this
 * element that matches the given search criteria.
 *
 * @param {!(webdriver.Locator|webdriver.By.Hash|Function)} locator The
 *     locator strategy to use when searching for the element.
 * @return {!webdriver.promise.Promise.<boolean>} A promise that will be
 *     resolved with whether an element could be located on the page.
 */
webdriver.WebElement.prototype.isElementPresent = function(locator) {
  return this.findElements(locator).then(function(result) {
    return !!result.length;
  });
};

elm.isPresent();

https://angular.github.io/protractor/#/api?view=ElementFinder.prototype.isPresent

/**
 * Determine whether the element is present on the page.
 *
 * @view
 * <span>{{person.name}}</span>
 *
 * @example
 * // Element exists.
 * expect(element(by.binding('person.name')).isPresent()).toBe(true);
 *
 * // Element not present.
 * expect(element(by.binding('notPresent')).isPresent()).toBe(false);
 *
 * @return {ElementFinder} which resolves to whether
 *     the element is present on the page.
 */
ElementFinder.prototype.isPresent = function() {
  return this.parentElementArrayFinder.getWebElements().then(function(arr) {
    if (arr.length === 0) {
      return false;
    }
    return arr[0].isEnabled().then(function() {
      return true; // is present, whether it is enabled or not
    }, function(err) {
      if (err.code == webdriver.error.ErrorCode.STALE_ELEMENT_REFERENCE) {
        return false;
      } else {
        throw err;
      }
    });
  }, function(err) {
    if (err.code == webdriver.error.ErrorCode.NO_SUCH_ELEMENT) {
      return false;
    } else {
      throw err;
    }
  });
};

elm.isElementPresent();

https://angular.github.io/protractor/#/api?view=ElementFinder.prototype.isElementPresent

/**
 * Same as ElementFinder.isPresent(), except this checks whether the element
 * identified by the subLocator is present, rather than the current element 
 * finder. i.e. `element(by.css('#abc')).element(by.css('#def')).isPresent()` is
 * identical to `element(by.css('#abc')).isElementPresent(by.css('#def'))`.
 *
 * @see ElementFinder.isPresent
 *
 * @param {webdriver.Locator} subLocator Locator for element to look for.
 * @return {ElementFinder} which resolves to whether
 *     the subelement is present on the page.
 */
ElementFinder.prototype.isElementPresent = function(subLocator) {
  if (!subLocator) {
    throw new Error('SubLocator is not supplied as a parameter to ' + 
      '`isElementPresent(subLocator)`. You are probably looking for the ' + 
      'function `isPresent()`.');
  }
  return this.element(subLocator).isPresent();
};

Comments

[Ardesco]

Whoever downvoted this tell us why, the answer looks good to me.

[Michael Radionov]

I think downvotes are for just copy-pasting source code without explaining anything.

[alecxe]

That's the kind of answer I was hoping to get. Thank you very much! I find these 3 ways of presence check quite confusing since there are actually differences between the methods and it's kind of unclear what the differences are by just looking to how the methods are named. Plus, the differences are not properly documented. Hope this answer just filled the gap and would help others in the future.

[alecxe]

Haven't downvoted but haven't upvoted either. I think Michael is certainly right about the downvote reasons. Thank you for participating and looking into this anyway!

[alecxe]

Thanks! That's the problem - there are actually 3 ways to do that in protractor and this is what the question is about.

[JeffC]

I did explain that two were equivalents... the rest I figured was pretty self-explanatory from the source. These are like 2- to 3-liner functions, excluding the error code in elm.isPresent(). shrugs