FileReader: error event

Syntax

Use the event name in methods like addEventListener(), or set an event handler property.

addEventListener("error", (event) => { })

onerror = (event) => { }

Event type

A ProgressEvent. Inherits from Event.

Event properties

Also inherits properties from its parent Event.

ProgressEvent.lengthComputable Read only

A boolean flag indicating if the total work to be done, and the amount of work already done, by the underlying process is calculable. In other words, it tells if the progress is measurable or not.

ProgressEvent.loaded Read only

A 64-bit unsigned integer value indicating the amount of work already performed by the underlying process. The ratio of work done can be calculated by dividing total by the value of this property. When downloading a resource using HTTP, this only counts the body of the HTTP message, and doesn't include headers and other overhead.

ProgressEvent.total Read only

A 64-bit unsigned integer representing the total amount of work that the underlying process is in the progress of performing. When downloading a resource using HTTP, this is the Content-Length (the size of the body of the message), and doesn't include the headers and other overhead.

Examples

const fileInput = document.querySelector('input[type="file"]');
const reader = new FileReader();

function handleSelected(e) {
  const selectedFile = fileInput.files[0];
  if (selectedFile) {
    reader.addEventListener("error", () => {
      console.error(`Error occurred reading file: ${selectedFile.name}`);
    });

    reader.addEventListener("load", () => {
      console.log(`File: ${selectedFile.name} read successfully`);
    });

    reader.readAsDataURL(selectedFile);
  }
}

fileInput.addEventListener("change", handleSelected);

Specifications

Browser compatibility

See also

• Related events: loadstart, loadend, progress, load, abort