为什么我在javascript中添加2 + 4时会得到24 [英] why do I get 24 when adding 2 + 4 in javascript
问题描述
我正在尝试这个:
function add_things() {
var first = '2';
var second = '4';
alert(first + second);
}
但它给了我24而不是6,我做错了什么?
But it gives me 24 instead of 6, what am I doing wrong?
推荐答案
您使用+运算符连接两个字符串。尝试:
You're concatenating two strings with the + operator. Try either:
function add_things() {
var first = 2;
var second = 4;
alert(first + second);
}
或
function add_things() {
var first = '2';
var second = '4';
alert(parseInt(first, 10) + parseInt(second, 10));
}
或
function add_things() {
var first = '2';
var second = '4';
alert(Number(first) + Number(second));
}
注意:第二种情况只适用于你从一个属性或用户输入中得到字符串。如果它们是你定义的常量,你想要添加它们然后将它们定义为整数(如第一个例子中所示)。
Note: the second is only really appropriate if you're getting strings from say a property or user input. If they're constants you're defining and you want to add them then define them as integers (as in the first example).
另外,正如所指出的,八进制是邪恶的。 parseInt('010')
实际上将以数字8(八进制中的10为8)出现,因此指定10的基数是个好主意。
Also, as pointed out, octal is evil. parseInt('010')
will actually come out as the number 8 (10 in octal is 8), hence specifying the radix of 10 is a good idea.
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