How Can I Preview Images Before Upload in a Browser Without Using Ajax?

Previewing Images Before Upload in the Browser

In the world of web development, it is often desirable to provide users with a preview of the images they are uploading before committing to the upload process. This functionality can significantly enhance the user experience by providing visual feedback and allowing them to make informed decisions about the images they wish to share.

Implementing Image Preview without Ajax

Achieving image previews without using Ajax involves utilizing the File API, which provides a browser-based interface for interacting with files. The following steps outline how to implement image preview functionality using this approach:

1. Event Handler for File Input:

   • Add an event listener to the file input element that triggers a function when a file is selected.

2. Create Object URL:

   • Within the event handler, use the URL.createObjectURL() method to create a URL that represents the selected file.

3. Assign URL to Image Source:

   • Retrieve the element where the preview will be displayed.
   • Set the src attribute of the element to the URL created in step 2.

Example Code:

The following code exemplifies the steps described above:

imgInp.onchange = evt => {
  const [file] = imgInp.files;
  if (file) {
    blah.src = URL.createObjectURL(file);
  }
};

<form runat="server">
  <input accept="image/*" type='file'>

By implementing this technique, developers can provide their users with a seamless and convenient image preview experience without the need for server-side interactions.

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