Simple Javascript I don't know how to put the functions in the if-else statements

Hi please help me my code is almost complete but it only triggers the last button which is the square root option. It's supposed to look like a calculator which opens up a pop-up button with a text box where you can input your numbers. I cannot trigger the right operation.

<input type="button" value="Add" onclick="calculate('addition')">
<input type="button" value="Subtract" onclick="calculate('subtraction')">
<input type="button" value="Multiply" onclick="calculate('multiplication')">
<input type="button" value="Divide" onclick="calculate('division')">
<input type="button" value="Modulo" onclick="calculate('modulo')">
<input type="button" value="Pow" onclick="calculate('pow')">
<input type="button" value="Factorial" onclick="calculate('factorial')">
<input type="button" value="Sqrt" onclick="calculate('sqrt')">


<script>
function calculate(addition)    {
    var x= prompt("What is your first number?", "");
    var y= prompt("What is your second number?", "");
    var z= parseInt(x)+parseInt(y);
    document.getElementById("z").value = z;
    }
function calculate(subtraction) {
    var x= prompt("What is your first number?", "");
    var y= prompt("What is your second number?", "");
    var z= parseInt(x)-parseInt(y);
    document.getElementById("z").value = z;
}

function calculate(multiplication)  {
    var x= prompt("What is your first number?", "");
    var y= prompt("What is your second number?", "");
    var z= parseInt(x)*parseInt(y)
    document.getElementById("z").value = z;
}

function calculate(division)    {
    var x= prompt("What is your first number?", "");
    var y= prompt("What is your second number?", "");
    var z= parseInt(x)/parseInt(y)
    document.getElementById("z").value = z;
}
function calculate(modulo)  {
    var x= prompt("What is your first number?", "");
    var y= prompt("What is your second number?", "");
    var z= parseInt(x)%parseInt(y)
    document.getElementById("z").value = z;
}

function calculate(pow) {
    var x= prompt("What is your first number?", "");
    var y= prompt("Raised to?", "");
    var i=1
    while (i<(parseInt(y)+1))   {
        var z= parseInt(x)*parseInt(x)
        i=parseInt(i)+1
        }
    document.getElementById("z").value = z;
}
function calculate(factorial)   {
    var x= prompt("What is your number?", "");
    var i=1
    var m=1
    while (m<(parseInt(x))) {
        i=parseInt(i)*((parseInt(m)+1))
        m=parseInt(m)+1
    }
    document.getElementById("z").value = i;
}
function calculate(sqrt)    {
    var x= prompt("What is your number?", "");
    i=1
    while (i%parseInt(x)!=0)    {
        z=(parseInt(x)%i)
        i=parseInt(i)+1
    }
    z=Math.sqrt(parseInt(x))
    document.getElementById("z").value = z;
}


</script>