Preview image before uploading

We input and img Element preparation tag for previewing the selected file .

<input type="file" id="fileInput" />

<img id="preview" />

Both of these elements can be passed through the following getElementById() Method to get ：

const fileEle = document.getElementById('fileInput');
const previewEle = document.getElementById('preview');

1. Use URL.createObjectURL() Method

fileEle.addEventListener('change', function (e) {
    // Get the selected file
    const file = e.target.files[0];

    // Create a new URL that references to the file
    const url = URL.createObjectURL(file);

    // Set the source for preview element
    previewEle.src = url;
});

2. Use FileReader Of readAsDataURL() Method

fileEle.addEventListener('change', function (e) {
    // Get the selected file
    const file = e.target.files[0];

    const reader = new FileReader();
    reader.addEventListener('load', function () {
        // Set the source for preview element
        previewEle.src = reader.result;
    });

    reader.readAsDataURL(file);
});