Category: JavaScript Answers

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JavaScript Answers

How to call a JavaScript function after script is loaded?

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You have a couple of options to call a JavaScript function after a script is loaded:

1. Inline Script

Place the function call directly after the script tag in your HTML file. This ensures that the function is called immediately after the script is loaded.

```html
<script src="your_script.js"></script>
<script>
    // Call your function here
    yourFunction();
</script>
```
</code></pre>
<h3>2. Event Listener</h3>
<p>Use the <code>DOMContentLoaded</code> event or <code>load</code> event to call the function when the DOM content or the entire page is loaded, respectively.</p>
<pre><code>```html
<script src="your_script.js"></script>
<script>
    document.addEventListener("DOMContentLoaded", function() {
        // Call your function here
        yourFunction();
    });
</script>
```
</code></pre>
<h3>3. Async/Await with Promises</h3>
<p>If your script is loaded asynchronously, you can use async/await with promises to ensure that the function is called after the script is loaded.</p>
<pre><code>```html
<script>
    async function loadScript(url) {
        let script = document.createElement('script');
        script.src = url;

        await new Promise((resolve, reject) => {
            script.onload = resolve;
            script.onerror = reject;
            document.head.appendChild(script);
        });
    }

    async function callFunctionAfterScriptLoaded() {
        await loadScript('your_script.js');
        // Call your function here
        yourFunction();
    }

    callFunctionAfterScriptLoaded();
</script>
```

Choose the method that best fits your use case and coding style.

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JavaScript Answers

How to get an element’s padding value using JavaScript?

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To get an element’s padding values using JavaScript, you can use the window.getComputedStyle() method.

To do this we write:

<!DOCTYPE html>
<html>
<head>
  <title>Get Element's Padding</title>
  <style>
    #myElement {
      padding: 20px;
      background-color: lightblue;
    }
  </style>
</head>
<body>

<div id="myElement">This is a div element.</div>

<script>
  // Get the element
  var element = document.getElementById("myElement");

  // Get the computed style of the element
  var computedStyle = window.getComputedStyle(element);

  // Get the padding values
  var paddingTop = computedStyle.getPropertyValue('padding-top');
  var paddingRight = computedStyle.getPropertyValue('padding-right');
  var paddingBottom = computedStyle.getPropertyValue('padding-bottom');
  var paddingLeft = computedStyle.getPropertyValue('padding-left');

  // Log the padding values
  console.log("Padding Top:", paddingTop);
  console.log("Padding Right:", paddingRight);
  console.log("Padding Bottom:", paddingBottom);
  console.log("Padding Left:", paddingLeft);
</script>

</body>
</html>

In this example, we first get the element by its ID using document.getElementById().

Then, we use window.getComputedStyle() to get the computed style of the element, which includes all styles applied to the element, including padding.

Finally, we use getPropertyValue() method to retrieve the values of padding-top, padding-right, padding-bottom, and padding-left properties.

Keep in mind that the values returned by window.getComputedStyle() are in pixels (px) by default, but you can use additional functions to convert them to other units if needed.

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JavaScript Answers

How to detect when position: sticky is triggered with JavaScript?

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To detect when an element’s position: sticky behavior is triggered using JavaScript, you can utilize the Intersection Observer API.

This API allows you to observe changes in the intersection of a target element with an ancestor element or viewport.

For example we write:

HTML:

<div id="stickyElement" style="position: sticky; top: 0;">
  Sticky Element
</div>

JavaScript:

// Target element with sticky positioning
var stickyElement = document.getElementById('stickyElement');

// Intersection Observer options
var options = {
  root: null, // use the viewport as the root
  threshold: 1.0 // fully visible
};

// Intersection Observer callback function
var callback = function(entries, observer) {
  entries.forEach(function(entry) {
    // Check if the target element is intersecting with the root
    if (entry.isIntersecting) {
      console.log('Sticky element is sticky now!');
      // Trigger our desired action when the sticky behavior is triggered
    } else {
      console.log('Sticky element is no longer sticky!');
      // Trigger our desired action when the sticky behavior is no longer active
    }
  });
};

// Create an Intersection Observer instance
var observer = new IntersectionObserver(callback, options);

// Start observing the target element
observer.observe(stickyElement);

In this example, we create an IntersectionObserver that watches the target element with the position: sticky behavior (stickyElement).

When the threshold is reached, indicating that the target element is fully visible within its containing element (or viewport if root is set to null), the callback function is triggered.

We can then perform our desired actions based on whether the sticky behavior is active or not.

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JavaScript Answers

How to change placeholder text with JavaScript?

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You can change the placeholder text of an input element using JavaScript by accessing its placeholder attribute and assigning a new value to it.

To do this we write

<input type="text" id="myInput" placeholder="Original Placeholder">

<script>
// Get the input element
var inputElement = document.getElementById("myInput");

// Change the placeholder text
inputElement.placeholder = "New Placeholder";
</script>

In this example, the placeholder text of the input element with the ID “myInput” is changed from “Original Placeholder” to “New Placeholder” using JavaScript.

You can also use the setAttribute method to achieve the same result:

// Change the placeholder text using setAttribute method
inputElement.setAttribute("placeholder", "New Placeholder");

Both methods accomplish the same thing; choose the one that you find more readable or suitable for your code structure.

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JavaScript Answers

How to stop scrolling child div from scrolling the window with JavaScript?

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To prevent a child div from scrolling the window when you’re scrolling inside it, you can use JavaScript to intercept the scroll event on the child div and stop the event propagation to the window.

To do this we can write:

<div id="parentDiv" style="overflow: auto; height: 200px;">
    <div id="childDiv" style="height: 400px;">
        <!-- Content of the child div -->
    </div>
</div>

<script>
var parentDiv = document.getElementById("parentDiv");
var childDiv = document.getElementById("childDiv");

childDiv.addEventListener("wheel", function(e) {
    e.stopPropagation(); // Stop the scroll event from bubbling up to the parent div
});
</script>

In this example, the wheel event is used, which is triggered when the user scrolls with a mouse wheel or similar input device.

Adjust the event listener based on your needs (e.g., scroll event for scrolling with scrollbar).

This code prevents the scroll event from reaching the parent div (parentDiv) when scrolling inside the child div (childDiv), effectively preventing the window from scrolling when you scroll inside the child div.