带提示的两个数字的总和(初学者JavaScript) [英] Sum of two numbers with prompt (Beginner JavaScript)
问题描述
我是JavaScript的新手,我正在学习这门语言的基础知识。
I'm new to JavaScript and I'm learning the basics of this language.
过去几天我一直试图解决这个问题:当我通过提示减去,乘以或除2输入数字时,一切正常;但是当我想添加它们时,我只能将两个数字简单地写在一起。
I've been trying to solve this problem for the last couple days: when I subtract, multiply or divide 2 numbers input through a prompt, everything works fine; but when I want to add them, I get the 2 numbers simply written together.
示例:如果我加5和6,我得到56 !!
Example: if I add 5 and 6, I get 56!!
这是我正在使用的代码。
Here's the code I'm working with.
var a = prompt("Enter first number");
var b = prompt("Enter second number");
alert(a + b);
我做错了什么?我是否必须指定值类型?
What am I doing wrong? Do I have to specify the value type?
推荐答案
函数提示
返回一个字符串并且 +
(不明智地,可能)用于两个字符串连接和数字添加。
The function prompt
returns a string and +
is (unwisely, perhaps) used for both string concatenation and number addition.
您没有在JavaScript中指定类型,但可以在运行时执行字符串到数字的转换。有很多方法可以做到这一点。最简单的是:
You do not "specify types" in JavaScript but you can do string to number conversion at run time. There are many ways to so this. The simplest is:
var a = +prompt("Enter first number");
var b = +prompt("Enter second number");
alert(a + b);
但你也可以
var a = Number(prompt("Enter first number"));
var b = Number(prompt("Enter second number"));
alert(a + b);
(避免 parseInt
因为它只处理前导字符,不会添加4.5和2.6之类的数字。)
(Avoid parseInt
because it only handles the leading characters and will not add numbers like 4.5 and 2.6.)
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