fastest way to detect if duplicate entry exists in javascript array?

Question

var arr = [\'test0\',\'test2\',\'test0\'];

Like the above,there are two identical entries with value \"test0\",how to check it most efficiently?

Answer 1

    var index = myArray.indexOf(strElement);
    if (index < 0) {
        myArray.push(strElement);
        console.log("Added Into Array" + strElement);
    } else {
        console.log("Already Exists at " + index);
    }