Return 语句未按预期工作

Question

So I was working with this line of code to convert an input image into an URL, however, the return doesn't seem to be working as I can't access the constant anywhere else in the document where I actually need it.

window.addEventListener('load', function() {
            document.querySelector('input[type="file"]').addEventListener('change', function() {
                if (this.files && this.files[0]) {
                    const imageURL = URL.createObjectURL(this.files[0]);
                    return imageURL;
                }
            });
          });       

I'm still new to JavaScript so for the life of me I can't find why it doesn't work, thanks in advance!

Answer 1

That's because constant imageURL is scoped in if block, if you want it to be accessed in whole file declare it outside addEventListener() function. For eg

let imageURL;
window.addEventListener('load', function() {
            document.querySelector('input[type="file"]').addEventListener('change', function() {
                if (this.files && this.files[0]) {
                    imageURL = URL.createObjectURL(this.files[0]);
                    
                }
            });
          });

console.log(imageURL)