Javascript 如何将 document.getElementById 值变成整数变量，而不是字符串？

How to make a document.getElementById value into an integer variable, not a string?

提问by Hales_W

I want to pass in a value, obtained from the an html object, convert that value into an integer so I can run arithmetic on it before outputting it. As my code stands now, it just adds them up like a string. So a value of 5 + a modifier of 100 ends up equaling = 5100, not 105.

我想传入一个从 html 对象获得的值，将该值转换为整数，以便我可以在输出之前对其进行算术运算。就我现在的代码而言，它只是将它们像字符串一样加起来。因此，值 5 + 修饰符 100 最终等于 = 5100，而不是 105。

Here's my form code:

这是我的表单代码：

<form>
    Add Amount: <select id="addTweets">
    <option value=5>5</option>
    <option value=10>10</option>
    <option value=15>15</option>
    </select>
    </br>
    <input type="button" value="Add It" onclick="addTweet()" />
</form>

Here's my script:

这是我的脚本：

function addTweet()
{
var mod = 100;
var results = document.getElementById("addTweets").value;
results += mod;

document.getElementById("tweetsOutput").innerHTML = results;
}

回答by 0x499602D2

The unary plus (+) coerces its operand into a number:

一元加号 ( +) 将其操作数强制转换为数字：

var results = +document.getElementById("addTweets").value;
    ...

typeof( results ); // number

回答by The Alpha

You can use parseInt

您可以使用 parseInt

var results = parseInt(document.getElementById("addTweets").value);

回答by davidethell

Use parseInt:

使用 parseInt：

var results = document.getElementById("addTweets").value;
var intResults = parseInt(results, 10) + mod;

回答by Kokizzu

just add parseInt, then you could add it normally

只需添加parseInt，然后您就可以正常添加它

 var results = parseInt(document.getElementById("addTweets").value);

EDIT:

编辑：

parseInt alternate, you can use "|0" use bitwise-or zero

parseInt 替代，您可以使用“|0”使用按位或零

 var results = document.getElementById("addTweets").value|0;

回答by ngunha02

Try:

尝试：

var valResult = document.getElementById("addTweets").value; // get the value of the field

var results = parseInt(valResult) + mod; // convert the value to int to do calculation

document.getElementById("addTweets").value = results; // assign results to the field value

回答by SaidbakR

Generally, you can convert the string numerical values into integers by doing a mathematical operation on it:

通常，您可以通过对其进行数学运算将字符串数值转换为整数：

x = "9"; //String numerical value
y = 10;//integer value
alert(x+y)// output 910;
x = x*1;
alert(x+y) // output 19

Checkout this demo

结帐这个演示