jQuery how to check if uploaded file is an image without checking extensions?

Question

Newbie here. The problem is that I currently have written a method which checks uploaded file size and extension in order to validate it. However, checking extensions is not a s

Answer 1

What I want to do is to check the actual file type

Try accessing files[0].type property . See Using files from web applications

$(":file").on("change", function(e) {

  console.log(this.files[0].type);
  
})

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<input type='file' id='imageLoader' name='imageLoader' accept="image/*" data-type='image' />

Answer 2

If anyone comes here who is using jQuery Validator, a simple method would be:

jQuery.validator.addMethod(
    "onlyimages",
    function (value, element) {
        if (this.optional(element) || !element.files || !element.files[0]) {
            return true;
        } else {
            var fileType = element.files[0].type;
            var isImage = /^(image)\//i.test(fileType);
            return isImage;
        }
    },
    'Sorry, we can only accept image files.'
);

which is then added to the .validate() function.

Answer 3

Pls refer a related query here. The answer here suggests to load the image in an Image object and check for it's width and height properties to be non zero. I think the technique can be used to solve your problem too.

I also worked out a fiddle for you to refer. Pertinent code below:

var img = new Image();
img.addEventListener("load",function(){
  alert('success');
});
img.addEventListener("error",function(){
      alert('error');
});
  img.src = picFile.result; 

Answer 4

You don't need jquery here.

var mimeType=this.files[0]['type'];//mimeType=image/jpeg or application/pdf etc...


//ie image/jpeg will be ['image','jpeg'] and we keep the first value
    if(mimeType.split('/')[0] === 'image'){
       console.log('the file is image');
    }

You can also create a function to check when a file is image.

function isImage(file){
   return file['type'].split('/')[0]=='image');//returns true or false
}

 isImage(this.file[0]);

Update (es6)

using es6 includes method, makes it even more simple.

const isImage = (file) => file['type'].includes('image');

Answer 5

You could try to convert file type in string and after that slice this string like that:

if(String(file.type).slice(0, 6) === 'image/') {....some code}

Answer 6

Try something like this:

JavaScript

const file = this.files[0];
const  fileType = file['type'];
const validImageTypes = ['image/gif', 'image/jpeg', 'image/png'];
if (!validImageTypes.includes(fileType)) {
    // invalid file type code goes here.
}

jQuery

var file = this.files[0];
var fileType = file["type"];
var validImageTypes = ["image/gif", "image/jpeg", "image/png"];
if ($.inArray(fileType, validImageTypes) < 0) {
     // invalid file type code goes here.
}