How can we use Async/Await to safely retrieve image dimensions from a callback-based function?

Creating Promises from Callbacks with Async/Await

The provided function, getImageData, utilizes callbacks to retrieve image dimensions upon loading. However, the synchronous nature of JavaScript may result in undefined values if the image is not fully loaded before accessing its properties.

To address this, we can leverage promises and async/await to guarantee the availability of the width and height before using them.

Converting the Callback to a Promise

The first step is to convert the getImageData function into a promise. This can be achieved using the Promise constructor:

<code class="javascript">function loadImage(url) {
  return new Promise((resolve, reject) => {
    const img = new Image();
    img.addEventListener('load', () => resolve(img));
    img.addEventListener('error', reject); // Handle errors
    img.src = url;
  });
}</code>

Utilizing Async/Await

With the loadImage function as a promise, we can use async/await to ensure the image is loaded before accessing its dimensions:

<code class="javascript">async function getImageData(url) {
  const img = await loadImage(url);
  return { width: img.naturalWidth, height: img.naturalHeight };
}
async function ready() {
  console.log(await getImageData(this.url))
}</code>

This version returns a promise that resolves with the image dimensions only when the image has finished loading. The ready function can now log these dimensions without encountering undefined values.

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