javascript。 将变量传递到变量输入字段

Question

I have a price calculator with multiple input fields but the calculation remains the same. What I have is this:

function calcone() {
    calc(Number(document.calc.priceboxa.value),
         Number(document.calc.amountboxa.value),
         document.calc.answera.value,);
}

function calctwo() {
    calc(Number(document.calc.priceboxb.value),
         Number(document.calc.amountboxb.value),
         document.calc.answerb.value,);
}

function calc(price, amount, costbox) {
    var one = price / amount,
    costbox = one;
}

I can't get "costbox = one;" to send the variable back to the answer* fields. What am I doing wrong? I've searched and can't find an answer to this.

New code that works:

function calcone() {
    calc(Number(document.calc.priceboxa.value),
         Number(document.calc.amountboxa.value),
         document.calc.answera,);
}

function calctwo() {
    calc(Number(document.calc.priceboxb.value),
         Number(document.calc.amountboxb.value),
         document.calc.answerb,);
}

function calc(price, amount, costbox) {
    var one = price / amount,
    costbox.value = one;
}

Answer 1

When you pass document.calc.answerb.value into your function as costbox it's like writing an address on a piece of paper and saying costbox will know where to find document.calc.answerb.value

So when you do:

costbox = one;

All you've done is rewritten the address on that sheet of paper. You haven't changed the value of document.calc.answerb.value which costbox used to point to; instead, you just told costbox to point to something else.

So what you have to do is actually change what costbox is pointing to...not the costbox itself. The question now is how do you resolve this? The answer is that instead of changing the value of costbox, you change the properties of costbox.

This means that instead of passing in

document.calc.answerb.value

you pass in

document.calc.answerb

and do costbox.value = one

function calc(price, amount, costbox) {
    var one = price / amount,
    costbox.value = one;
}

Now instead of wiping that piece of paper clear of the address and writing down a new one, you're visiting the address and saying: "I want the value changed"

Answer 2

Your passing the value to the method not the element you need to do this:

function calcone() {
    calc(Number(document.calc.priceboxa.value), Number(document.calc.amountboxa.value));
}

function calc(price, amount) {
    var one = price / amount;
    document.calc.answera.value = one;
}

Or:

function calcone() {
    calc(Number(document.calc.priceboxa.value), Number(document.calc.amountboxa.value), document.calc.answera);
}

function calc(price, amount, answerbox) {
    var one = price / amount;
    answerbox.value = one;
}