A smarter scripter would recognize that the preceding scripts might fail in very old browsers, where script errors tend to be rather invasive. To prevent such errors, the author makes two modifications. First, the potentially offending script statements in the getImgAreas( ) function wrap themselves in an object detection block. Second, the main…

getImgAreas.js

function getImgAreas( ) {
 var result;
 // make sure browser supports img element objects
 if (document.images) {
 // initialize return value so we can add to it
 result = 0;
 // loop through all img objects on the page
 for (var i = 0; i < document.images.length; i++) {
 // accumulate image areas
 result += (document.images[i].width * document.images[i].height);
 }
 }
 // returned value is either a number or null
 return result;
}
function reportImageArea( ) {
 // grab result so we can verify it
 var imgArea = getImgAreas( );
 var output;
 if (imgArea == null) {
 // message for browsers not supporting img object
 output = "Unknown";
 } else {
 output = imgArea;
 }
 document.reportForm.imgData.value = output;
}