Using Selenium in Java, one can wait for a JavaScript event (such as onchange) to finish before proceeding

Question

Using Selenium in Java, one can wait for a JavaScript event (such as onchange) to finish before proceeding

When a group of interconnected input fields have an onchange event, the values in some fields are updated correctly while others are not due to interference from the onchange event.

Once the onchange event is triggered on a field, it initiates a process that involves other related fields. It stores the value somewhere and clears other related fields if they were not previously processed by their own onchange event.

I have considered pausing the thread for a set period of time, but this approach seems unreliable. It would involve guessing the processing time and deciding between idle waiting or risking script timeouts.

Is there a way to determine when the JavaScript code (called by the onchange event) has completed its tasks?

Original Code

Wait<WebDriver> wait = new WebDriverWait(driver, 25, 500);
for(int i = 1; i <= fieldCount; i++) {
    elementId = "field$" + i;
    wait.until(ExpectedConditions.elementToBeClickable(By.id(elementId)));
    driver.findElementById(elementId).sendKeys(data);
    //The mess happens if I don't sleep
    Thread.sleep(3000);
}

Output

With sleep: Field1:_w_ ... Field2:_x_ ... Field3:_y_ ... FieldN:_z_

Without sleep: Field1:_w_ ... Field2:___ ... Field3:_y_ ... FieldN:___

Notes:

While encountering issues, I learned valuable lessons which I feel are important to highlight:

WARNING: Do not mix implicit and explicit waits.

Prefer using WebDriverWait over FluentWait, unless you have very specific requirements. For example, WebDriverWait handles NotFoundException automatically. Refer to this recommendation.

javascript java selenium events onchange

Answer 1

Answer №1

After significant restructuring and thorough investigation, I successfully achieved my goal. The onchange event triggers when the value of the input field changes and the element no longer has focus. Utilizing WebElement methods like sendKeys() is not feasible due to lack of control over background processes, hence resorting to using JavascriptExecutor was necessary. Initially, I updated the field value with JavaScript (which does NOT initiate the event), followed by manually triggering the onchange event through JavaScript:

//To prevent interference with explicit waits, set implicit wait to 0
driver.manage().timeouts().implicitlyWait(0, TimeUnit.SECONDS);
//Utilize WebDriverWait instead of FluentWait for better results
Wait<WebDriver> wait = new WebDriverWait(driver, 25, 500);
for(int i = 1; i <= fieldCount; i++) {
    String elementId = "field$" + i;
    String javaScript = String.format("document.getElementById('%s').value='%s';", elementId , myValue);
    Object jsResult = wait.until(ExpectedConditions.javaScriptThrowsNoExceptions(javaScript));
    javaScript = String.format("return document.getElementById('%s').dispatchEvent(new Event('change'));", elementId);
    jsResult = wait.until(ExpectedConditions.jsReturnsValue(javaScript));
}

Several key points should be noted here.

Avoid mixing implicit and explicit waits as it can lead to unforeseen outcomes.
Prefer using WebDriverWait over its superclass FluentWait, unless a specific requirement dictates otherwise. If utilizing FluentWait, remember to handle the appropriate exceptions to avoid NoSuchElementException.
The onchange event triggers when the value of the input field changes and the element loses focus.
dispatchEvent() dispatches an Event synchronously at the specified EventTarget, invoking the affected EventListeners in proper sequence. This principle applies to custom events as well. For more details on events, refer to this resource.

To deepen understanding of

ExpectedConditions.javaScriptThrowsNoExceptions

and

ExpectedConditions.jsReturnsValue

, I employed the following JavaScript snippet that keeps the engine occupied for a short duration. This experiment sheds light on how explicit waits interact with JavaScript and allows inspection of return values. Notably, the JS code varies slightly between each ExpectedCondition:

//ExpectedConditions.jsReturnsValue
String javaScript = "(function watcher(ms){var start=new Date().getTime();var end = start;while(end<start+ms){end=new Date().getTime();};return 'complete';})(5000);return 'success';";
log.trace("javaScript={}", javaScript);
Object jsResult = wait.until(ExpectedConditions.jsReturnsValue(javaScript));
log.trace("jsResult={}", jsResult);

//ExpectedConditions.javaScriptThrowsNoExceptions
javaScript = "(function watcher(ms){var start=new Date().getTime();var end = start;while(end<start+ms){end=new Date().getTime();};return 'complete';})(5000);";
log.trace("javaScript={}", javaScript);
jsResult = wait.until(ExpectedConditions.javaScriptThrowsNoExceptions(javaScript));
log.trace("jsResult={}", jsResult);

Answer 2

After significant restructuring and thorough investigation, I successfully achieved my goal. The onchange event triggers when the value of the input field changes and the element no longer has focus. Utilizing WebElement methods like sendKeys() is not feasible due to lack of control over background processes, hence resorting to using JavascriptExecutor was necessary. Initially, I updated the field value with JavaScript (which does NOT initiate the event), followed by manually triggering the onchange event through JavaScript:

//To prevent interference with explicit waits, set implicit wait to 0
driver.manage().timeouts().implicitlyWait(0, TimeUnit.SECONDS);
//Utilize WebDriverWait instead of FluentWait for better results
Wait<WebDriver> wait = new WebDriverWait(driver, 25, 500);
for(int i = 1; i <= fieldCount; i++) {
    String elementId = "field$" + i;
    String javaScript = String.format("document.getElementById('%s').value='%s';", elementId , myValue);
    Object jsResult = wait.until(ExpectedConditions.javaScriptThrowsNoExceptions(javaScript));
    javaScript = String.format("return document.getElementById('%s').dispatchEvent(new Event('change'));", elementId);
    jsResult = wait.until(ExpectedConditions.jsReturnsValue(javaScript));
}

Several key points should be noted here.

Avoid mixing implicit and explicit waits as it can lead to unforeseen outcomes.
Prefer using WebDriverWait over its superclass FluentWait, unless a specific requirement dictates otherwise. If utilizing FluentWait, remember to handle the appropriate exceptions to avoid NoSuchElementException.
The onchange event triggers when the value of the input field changes and the element loses focus.
dispatchEvent() dispatches an Event synchronously at the specified EventTarget, invoking the affected EventListeners in proper sequence. This principle applies to custom events as well. For more details on events, refer to this resource.

To deepen understanding of

ExpectedConditions.javaScriptThrowsNoExceptions

and

ExpectedConditions.jsReturnsValue

, I employed the following JavaScript snippet that keeps the engine occupied for a short duration. This experiment sheds light on how explicit waits interact with JavaScript and allows inspection of return values. Notably, the JS code varies slightly between each ExpectedCondition:

//ExpectedConditions.jsReturnsValue
String javaScript = "(function watcher(ms){var start=new Date().getTime();var end = start;while(end<start+ms){end=new Date().getTime();};return 'complete';})(5000);return 'success';";
log.trace("javaScript={}", javaScript);
Object jsResult = wait.until(ExpectedConditions.jsReturnsValue(javaScript));
log.trace("jsResult={}", jsResult);

//ExpectedConditions.javaScriptThrowsNoExceptions
javaScript = "(function watcher(ms){var start=new Date().getTime();var end = start;while(end<start+ms){end=new Date().getTime();};return 'complete';})(5000);";
log.trace("javaScript={}", javaScript);
jsResult = wait.until(ExpectedConditions.javaScriptThrowsNoExceptions(javaScript));
log.trace("jsResult={}", jsResult);

Answer 3

Answer №2

Here is a helpful method that can be used to wait until JQuery becomes inactive:

/**
 * This method waits for JQuery to become inactive
 * @author Emma Smith
 */
public void awaitJQueryInactivity() {

    Boolean isJqueryUsed = (Boolean) ((JavascriptExecutor) driver)
            .executeScript("return (typeof(jQuery) != 'undefined')");

    if (isJqueryUsed) {
        while (true) {
            // Check if jQuery is still active with JavaScript test
            Boolean ajaxIsComplete = (Boolean) (((JavascriptExecutor) driver)
                    .executeScript("return jQuery.active == 0"));
            if (ajaxIsComplete)
                break;
            try {
                Thread.sleep(100);
            } catch (InterruptedException e) {
            }
        }
    }

}

Answer 4

Here is a helpful method that can be used to wait until JQuery becomes inactive:

/**
 * This method waits for JQuery to become inactive
 * @author Emma Smith
 */
public void awaitJQueryInactivity() {

    Boolean isJqueryUsed = (Boolean) ((JavascriptExecutor) driver)
            .executeScript("return (typeof(jQuery) != 'undefined')");

    if (isJqueryUsed) {
        while (true) {
            // Check if jQuery is still active with JavaScript test
            Boolean ajaxIsComplete = (Boolean) (((JavascriptExecutor) driver)
                    .executeScript("return jQuery.active == 0"));
            if (ajaxIsComplete)
                break;
            try {
                Thread.sleep(100);
            } catch (InterruptedException e) {
            }
        }
    }

}

Answer 5

Answer №3

This custom function is designed to wait for the web page to reach the "complete" state before continuing with any operations or actions.

/**
 * Custom method to ensure that the webpage has finished loading
 * @author Jack Johnson
 */
public void waitForPageToLoad() {

    WebDriverWait wait = new WebDriverWait(driver, 10);
    wait.until(new ExpectedCondition<Boolean>() {

        public Boolean apply(WebDriver wdriver) {
            return ((JavascriptExecutor) driver).executeScript("return document.readyState").equals("complete");
        }
    });
}

Answer 6

This custom function is designed to wait for the web page to reach the "complete" state before continuing with any operations or actions.

/**
 * Custom method to ensure that the webpage has finished loading
 * @author Jack Johnson
 */
public void waitForPageToLoad() {

    WebDriverWait wait = new WebDriverWait(driver, 10);
    wait.until(new ExpectedCondition<Boolean>() {

        public Boolean apply(WebDriver wdriver) {
            return ((JavascriptExecutor) driver).executeScript("return document.readyState").equals("complete");
        }
    });
}

Answer 7

Answer №4

According to my understanding, Selenium Web Driver does not have the capability to wait for asynchronous events. However, you can utilize WebDriverWait class to wait for the effects of those events. If the mentioned events result in changes to the DOM, you can detect these changes by using specific ExpectedConditions.

   Wait<WebDriver> wait = new WebDriverWait(driver, 15, 500);

   // here you make some change to the input

   wait.until(ExpectedConditions.elementToBeClickable(By.xpath("//input")));

In this example, the code will wait until a button becomes active. If the expected conditions are not met within 15 seconds, an exception will be thrown.

If the provided ExpectedConditions do not suffice, you have the option to create your own by implementing the ExpectedCondition interface. For further details, refer to the documentation.

https://seleniumhq.github.io/selenium/docs/api/java/org/openqa/selenium/package-summary.html https://seleniumhq.github.io/selenium/docs/api/java/org/openqa/selenium/support/ui/package-summary.html

Answer 8

According to my understanding, Selenium Web Driver does not have the capability to wait for asynchronous events. However, you can utilize WebDriverWait class to wait for the effects of those events. If the mentioned events result in changes to the DOM, you can detect these changes by using specific ExpectedConditions.

   Wait<WebDriver> wait = new WebDriverWait(driver, 15, 500);

   // here you make some change to the input

   wait.until(ExpectedConditions.elementToBeClickable(By.xpath("//input")));

In this example, the code will wait until a button becomes active. If the expected conditions are not met within 15 seconds, an exception will be thrown.

If the provided ExpectedConditions do not suffice, you have the option to create your own by implementing the ExpectedCondition interface. For further details, refer to the documentation.

https://seleniumhq.github.io/selenium/docs/api/java/org/openqa/selenium/package-summary.html https://seleniumhq.github.io/selenium/docs/api/java/org/openqa/selenium/support/ui/package-summary.html

Using Selenium in Java, one can wait for a JavaScript event (such as onchange) to finish before proceeding

Original Code

Output

Answer №1

Answer №2

Answer №3

Answer №4

Similar questions

Executing a particular Java class through POM.XML in relation to TestNG: A comprehensive guide

What is the best way to eliminate the nesting in this ternary operation?

What is the best way to manage zoom settings following a completed search query?

What could be causing my website's screen resolution to not fit properly on mobile devices?

Following my ajax submission, the functionality of my bootstrap drop-down menu seems to have been compromised

Having trouble binding form data to a React component with the onChange() method?

Explore the different features scenarios within cucumber

What mechanisms do frameworks use to update the Document Object Model (DOM) without relying on a

It appears that the Facebook share feature is not picking up any meta OG tags

Children components in Vue.js are receiving an undefined props object

Guide to indicating the chosen filter in React using Material UI

Is it possible to incorporate Nth child into JavaScript?

Is it possible to run a Vue file autonomously, similar to an HTML file

Socket.io is most effective when reconnecting

Tips for passing parameters in the $http GET request to transmit information from a dropdown menu using AngularJS

How to dynamically load a component within a class-based Vue component

Having trouble displaying options in VueJS Component using datalist

A guide to validating a v-edit-dialog within a v-datatable

HTML - Selecting Different Values in One Drop Down Based on Another Drop Down

Issue with HTML5 Canvas y-axis dimensions