Javascript 如何使用 window.prompt 在变量中获得数学表达式？

Question

I have this Code, which isn't working properly.我有这个代码，它不能正常工作。 As you can see i try to get a formula in to an array.如您所见，我尝试将公式放入数组中。 this is used to calculate the mathematical use later.这用于计算稍后的数学用途。 but the programm don't put the formula in the right form right where the var stands:但是程序没有将公式放在 var 所在的正确形式中：

<html>
<title> JavaScript Tutorial 1
</title>
<body>
<script language = "javascript">

var f, a, b, c, d, j, k, sum;

f = String(window.prompt("Formel"));
a = Number(window.prompt("untere grenze 1tes E"));
b = Number(window.prompt("obere grenze 1tes E"));
c = Number(window.prompt("untere grenze 2tes E"));
d = Number(window.prompt("obere grenze 2tes E"));





sum = 0;
for (j = a; j <= b; j++) {

    for (k = c ; k <= d ; k++) {
    sum += f;
    }
}

document.write(sum);

</script>
<noscript>
    <p> You have JavaScript Turned Off <p>
</noscript>
</body>
</html>

And i have this Code here, which calculate it right.我在这里有这个代码，它计算正确。 But i would like to get the formula in to a var over the window.promp但我想通过 window.promp 将公式放入 var

<html>
<title> JavaScript Tutorial 1
</title>
<body>
<script language = "javascript">

var f, a, b, c, d, j, k, sum;

//f = String(window.prompt("Formel"));
a = Number(window.prompt("untere grenze 1tes E"));
b = Number(window.prompt("obere grenze 1tes E"));
c = Number(window.prompt("untere grenze 2tes E"));
d = Number(window.prompt("obere grenze 2tes E"));

sum = 0;
for (j = a; j <= b; j++) {

    for (k = c ; k <= d ; k++) {
    sum += j * j * k;
    }
}

document.write(sum);

</script>
<noscript>
    <p> You have JavaScript Turned Off <p>
</noscript>
</body>
</html>

Answer 1

@ yellowsir, thank you for your input, it works well with eval and i understand the security lack. @ Yellowsir，感谢您的投入，它与 eval 配合良好，我了解安全性不足。 As i just use this project for my self there will be no risk of someone putting in some malcode ;)因为我只是为自己使用这个项目，所以不会有人输入一些恶意代码的风险；)

Here is the Solution i got out of your input:这是我从您的输入中得到的解决方案：

<html>
<title> JavaScript Tutorial 1
</title>
<body>
<script language = "javascript">

var f, a, b, c, d, j, k, sum;

a = Number(window.prompt("untere grenze 1tes E"));
b = Number(window.prompt("obere grenze 1tes E"));
c = Number(window.prompt("untere grenze 2tes E"));
d = Number(window.prompt("obere grenze 2tes E"));
f = window.prompt("Formel");

sum = 0;
for (j = a; j <= b; j++) {

    for (k = c ; k <= d ; k++) {
    sum += eval(f);
    }
}

// document.write("<br>")
document.write(sum);

</script>
<noscript>
<p> You have JavaScript Turned Off <p>
</noscript>
</body>
</html>

Hopefully everything is clear do not hesitate to ask.希望一切都清楚，不要犹豫，问。

Javascript 如何使用 window.prompt 在变量中获得数学表达式？

问题描述

1 个解决方案

解决方案1
0 已采纳 2015-09-23 11:24:22

Javascript 如何使用 window.prompt 在变量中获得数学表达式？

问题描述

1 个解决方案

解决方案1 0 已采纳 2015-09-23 11:24:22

解决方案1
0 已采纳 2015-09-23 11:24:22