jQuery code to validate input fields

form.html

<form id="uploadImages">
    <input type="file" id="fotos" multiple="true" /><br />
    <p class="callback">Try to upload some files here.</p>
    <input type="submit" name="Submit" />
</form>

validation.js

$("#uploadImages").on('submit', function(){
    var photos        = $('#fotos');
    var p             = $('.callback');
    var allowed_types = new Array(
        "application/pdf",
        "image/jpeg",
        "image/png"
    );
    
    // Just so you can check out the file object in the console
    console.log(photos);

    // Don't send it blank
    if(photos[0].files.length == 0) {
        p.html("You should upload at least 1 file.");
        return false;
    }
    
    // http://www.feedforall.com/mime-types.htm
    $.each(photos[0].files, function(index, file){
        
        // validates extensions    
        if( allowed_types.indexOf(file.type) !== 0 ) {
            p.html("You can only upload: pdf, jpg and png.");
            return false;
        }
        
        // validates size
        if( file.size > 1048576 ) {
            p.html("The max filesize is 1MB.");
            return false;
        }
        
    });
    
    return false;
});