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javascript - Get key char (value) from keycode with shift modifier

I have been lucky to find String.fromCharCode(). It has helped me significantly. However, I noticed it doesn't take into account the shift modifier. I know the event.shiftKey property and use it, but right now I need to get the key value (eg: "A" or "a") which takes into account the shift key modifier. At first I used String.toLowerCase().. But I neglected to think of number keys, to give one example: "5" (without shift) and "%" (with shift). I need to differentiate between the two in my program. What's an easy way to get the key char value?

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This brute force technique isn't the prettiest, but it seems to work. I'm in search of the same functionality.

function mapKeyPressToActualCharacter(isShiftKey, characterCode) {
    if ( characterCode === 27 || characterCode === 8 || characterCode === 9 || characterCode === 20 || characterCode === 16 || characterCode === 17 || characterCode === 91 || characterCode === 13 || characterCode === 92 || characterCode === 18 ) {
        return false;
    }
    if (typeof isShiftKey != "boolean" || typeof characterCode != "number") {
        return false;
    }
    var characterMap = [];
    characterMap[192] = "~";
    characterMap[49] = "!";
    characterMap[50] = "@";
    characterMap[51] = "#";
    characterMap[52] = "$";
    characterMap[53] = "%";
    characterMap[54] = "^";
    characterMap[55] = "&";
    characterMap[56] = "*";
    characterMap[57] = "(";
    characterMap[48] = ")";
    characterMap[109] = "_";
    characterMap[107] = "+";
    characterMap[219] = "{";
    characterMap[221] = "}";
    characterMap[220] = "|";
    characterMap[59] = ":";
    characterMap[222] = """;
    characterMap[188] = "<";
    characterMap[190] = ">";
    characterMap[191] = "?";
    characterMap[32] = " ";
    var character = "";
    if (isShiftKey) {
        if ( characterCode >= 65 && characterCode <= 90 ) {
            character = String.fromCharCode(characterCode);
        } else {
            character = characterMap[characterCode];
        }
    } else {
        if ( characterCode >= 65 && characterCode <= 90 ) {
            character = String.fromCharCode(characterCode).toLowerCase();
        } else {
            character = String.fromCharCode(characterCode);
        }
    }
    return character;
}

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