How can I check if my string contains a period in JavaScript?

var str="myfile.doc";
var str2="mydirectory";

if(str.indexOf('.') !== -1)
{
  // would be true. Period found in file name
  console.log("Found . in str")
}

if(str2.indexOf('.') !== -1)
{
  // would be false. No period found in directory name. This won't run.
  console.log("Found . in str2")
}