Javascript - how to browser to a folder?

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Javascript

I want to fI want to find a JS component to browser to a folder (Not a file). From https://stackoverflow.com/questions/43958335/select-folder-instead-of-single-file-input, someone uses the webkitdirectory. I have tried the code as shown below:

<input id="myInput" type="file" webkitdirectory directory multiple/>
// --------------------
HTMLInputElement.webkitdirectory = true;
var folder = document.getElementById("myInput");
folder.onchange = function () {
    var files = folder.files,
      len = files.length,
      i;
    for (i = 0; i < len; i += 1) {
        console.log(files[i]);
    }
}

However, the variable 'folder' is null. What's wrong in my code? Thanks.

What I have tried:

JavaScript - How to browser to a folder?