How to validate the upload file is excel or not in the client side

onBlur evernt use this code.

onblur="if(this.value.lastIndexOf(\'.xls\')==-1){ alert(\'Please upload only .xls extension file\'); return false;}"

for PDF file

onblur="if(this.value.lastIndexOf(\'.pdf\')==-1){ alert(\'Please upload only .xls extension file\'); return false;}"