JS - Validating file types

filetypeValidator.js

const fileExtArr = ["png", "jpeg", "tft", "bmp", "jpg"]; 
const maxFileSize = 4194587;

function validateUploadedFile(elementId) {
    let fileElement = getElement(elementId); 
    
    const ext = fileUploadJson.docType || ""; 
    
    if (ext == "" || fileExtArr.indexOf(ext.toLowerCase()) < 0)
    { 
        fileElement.parentElement.parentElement.nextElementSibling.innerHTML = "Please select a file type (PNG, JPEG, TFT, BPM, JPG, PDF)";

        disableLoader(); 
        return false; 
        
    } else if (parseInt(fileElement.getAttribute('fs')) > maxFileSize) { 
        
        fileElement.parentElement.parentElement.nextElementSibling.innerHTML = "File size exceeds 4MB. Kindly select a different file"; 
        
        disableLoader(); 
        return false; 
        
    } return true; 
}