我怎样才能让我的程序检查所选单词中是否有按下的键

Question

I'm working on a hangman game and I'm checking to see if the letter that the user guesses by the use of key down is in the randomly chosen saying. But it either always gives me the answer of "Yes it is in the saying" or "No it is not in the saying" no matter if the letter is actually in the saying or not. Any help much appreciated. Thankyou.

Here is the code I'm working with at the moment.

document.addEventListener("keydown", function textFunction(event)
{
if (event.keyCode > 64 && event.keyCode < 91) 
{
    var guess = event.keyCode;
    var a = "a";
    var letterGuess = String.fromCharCode(event.keyCode);
    if(sayings[randomSaying].contains(guess)){
        alert("yes");
    } else {
        alert("no");
    }
    alert(String.fromCharCode(event.keyCode));
} 
else 
{
    alert("Please type a letter");
}
});

And the randomly chosen saying

var sayings = [
    "cash on the nail",
    "charley horse",
    "double cross",
    "fit as a fiddle",
    "hands down",
    "if the cap fits",
    "mumbo jumbo",
    "see red",
    "stone the crows",
    "thick and thin",
]
sayings.toString();
var randomSaying = Math.floor(Math.random()*sayings.length);

Answer 1

The String.fromCharCode(event.keyCode); returns capital letter by default. As such, you'll never match.

EDIT: Clarification, the keyCodes supplied are the capitalized letter, so the String.fromCharCode will always return a capital letter by default.