Raw code:

function guessNumber() {
    let num = Math.floor(Math.random() * 100) + 1, userInput;
    do {
        userInput = Number(prompt("Guess a number between 1-100"));
        if (isNaN(userInput) || userInput < 0 || userInput > 100) {
            alert("Invalid input");
        }
        if (userInput < num) console.log("too low");
        else if (userInput > num) console.log("too high");
        else console.log("Congrats!! the number was" + num);
    } while (userInput !== num);
}

function calculator() {
    let userInput;
    do {
        let num1 = Number(prompt("Enter first number"));
        let num2 = Number(prompt("Enter second number"));
        let operator = prompt("Choose a valid operator +,-,*,/");

        switch (operator) {
            case '+':
                alert(`Addition of ${num1} and ${num2} is ${num1 + num2}`);
                break;
            case '-':
                alert(`Subtraction of ${num1} and ${num2} is ${num1 - num2}`);
                break;
            case '*':
                alert(`Multiplication of ${num1} and ${num2} is ${num1 * num2}`);
                break;
            case '/':
                if (num2 == 0) alert(Infinity);
                else alert(`Division of ${num1} and ${num2} is ${num1 / num2}`);
                break;
            default:
                alert("Enter a valid operator");
                break;
        }
        userInput = prompt("Do you want to try the calculator again? (yes/no)").toLowerCase();
    } while (userInput === "yes");
}
            

Optimized code

function guessNumber() {
    let num = Math.floor(Math.random() * 100) + 1, userInput;
    do {
        userInput = Number(prompt("Guess a number between 1-100"));
        if (isNaN(userInput) || userInput < 1 || userInput > 100) alert("Invalid input");
        else if (userInput < num) console.log("Too low");
        else if (userInput > num) console.log("Too high");
        else console.log(`Congrats!! The number was ${num}`);
    } while (userInput !== num);
}

function calculator() {
    let userInput;
    do {
        let num1 = Number(prompt("Enter first number")), num2 = Number(prompt("Enter second number"));
        let operator = prompt("Choose a valid operator (+, -, *, /)");

        let result = operator === '+' ? num1 + num2 :
                    operator === '-' ? num1 - num2 :
                    operator === '*' ? num1 * num2 :
                    operator === '/' ? (num2 === 0 ? "Infinity" : num1 / num2) :
                    "Invalid operator";

        alert(result !== "Invalid operator" ? `${num1} ${operator} ${num2} = ${result}` : result);
        userInput = prompt("Do you want to try the calculator again? (yes/no)").toLowerCase();
    } while (userInput === "yes");
}