js check file extension input file code example

Example 1: javascript - get the filename and extension from input type=file

//Use lastIndexOf to get the last \ as an index and use substr to get the remaining string starting from the last index of \

function getFile(filePath) {
        return filePath.substr(filePath.lastIndexOf('\\') + 1).split('.')[0];
    }

    function getoutput() {
        outputfile.value = getFile(inputfile.value);
        extension.value = inputfile.value.split('.')[1];
    }
<input id='inputfile' type='file' name='inputfile' onChange='getoutput()'><br>
    Output Filename <input id='outputfile' type='text' name='outputfile'><br>
    Extension <input id='extension' type='text' name='extension'>

Example 2: javascript - get the filename and extension from input type=file

//Use lastIndexOf to get the last \ as an index and use substr to get the remaining string starting from the last index of \


function getFileNameWithExt(event) {

  if (!event || !event.target || !event.target.files || event.target.files.length === 0) {
    return;
  }

  const name = event.target.files[0].name;
  const lastDot = name.lastIndexOf('.');

  const fileName = name.substring(0, lastDot);
  const ext = name.substring(lastDot + 1);

  outputfile.value = fileName;
  extension.value = ext;
  
}
<input id='inputfile' type='file' name='inputfile' onChange='getFileNameWithExt(event)'><br>
  Output Filename <input id='outputfile' type='text' name='outputfile'><br>
  Extension <input id='extension' type='text' name='extension'>