Is it possible to check and validate file type on presubmit ?

Currently in my form I'm checking whether or not the field has a value and also length but I'm wondering if there's a way to check the file type on uploads as well?

This is my code for the presubmit >

editor.on( 'preSubmit', function ( e, o, action ) {
     if ( action !== 'remove' ) {
         var numOfFields = $('[data-editor-template]').length;
         var fieldNames = Object.keys(this.s.fields);
         var skip = ['home_sections.status_id','home_sections.section_image_id','home_sections.link'];
         for(var i=0;i<numOfFields;i++){

          if(fieldNames[i] == "home_sections.section_image_id"){
              console.log(this.field(fieldNames[i]));
              this.field(fieldNames[i]).error('This field can not be over 200 characters');
             }

            if(fieldNames[i] == "home_sections.link" && this.field(fieldNames[i]).val().length >= 200 ){
              this.field(fieldNames[i]).error('This field can not be over 200 characters');
             }

             else {
                if (skip.includes(fieldNames[i])) {
                 continue;
               }
             }

             if(fieldNames[i] == "home_sections.title" && this.field(fieldNames[i]).val().length >= 75 ){
              this.field(fieldNames[i]).error('This field can not be over 75 characters');
             }


             if( !this.field(fieldNames[i]).val() ) {
                  this.field(fieldNames[i]).error('This field can not be empty');
             }
         }

         if ( this.inError() ) {
             return false;
         }
     }
 } );