Javascript 将 +1 添加到只读文本输入字段的 jQuery 值
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Adding +1 to jQuery value of a readonly text input field
提问by Dnaso
I am using a function where I have a readonlytext input, and when I execute the function I want the number value + 1. So let's say I have 60, when I execute the function, the number returned should be 61.
我正在使用一个有readonlytextinput的函数，当我执行该函数时，我想要数字值 + 1。所以假设我有 60，当我执行该函数时，返回的数字应该是 61。
But instead it's coming out 601, which is just adding the number 1 to the string. Any clue as to what is going on? Subtraction, multiplication and division all work fine. Here is a snippet
但是它出来的是 601，它只是将数字 1 添加到字符串中。关于发生了什么的任何线索？减法、乘法和除法都可以正常工作。这是一个片段
var num= $("#originalnum").val() + 1;
$("#originalnum").val(num);
And yes i've tried a few different variations, am I missing something?
是的，我尝试了一些不同的变体，我错过了什么吗？
回答by Eric
A simple unary +is sufficient to turn a string into a number in this case:
+在这种情况下，简单的一元足以将字符串转换为数字：
var num = +$("#originalnum").val() + 1;
$("#originalnum").val(num);
回答by nnnnnn
The problem is that .val()returns the value of the element as a string, and when you use the +operator on a string it does string concatenation. You need to convert the value to a number first:
问题是.val()将元素的值作为字符串返回，当您+在字符串上使用运算符时，它会进行字符串连接。您需要先将值转换为数字：
var num = +$("#originalnum").val() + 1; // unary plus operator
// OR
var num = Number($("#originalnum").val()) + 1; // Number()
// OR
var num= parseFloat($("#originalnum").val()) + 1; // parseFloat()
// OR
var num= parseInt($("#originalnum").val(),10) + 1; // parseInt()
Note that if you use parseInt()you mustinclude the radix (10) as the second parameter or it will (depending on the browser) treat strings with a leading zero as octal and strings with a leading "0x"as hexadecimal. Note also that parseInt()ignores any non-numeric characters at the end of the string, including a full-stop that the user might have intended as a decimal point, so parseInt("123.45aasdf",10)returns 123. Similarly parseFloat()ignores non-numeric characters at the end of the string.
请注意，如果你使用parseInt()，你必须包括基数（10）作为第二个参数，否则会（视浏览器）治疗用字符串作为八进制和字符串前导零与一家领先的"0x"为十六进制。另请注意，parseInt()忽略字符串末尾的任何非数字字符，包括用户可能希望作为小数点的句号，因此parseInt("123.45aasdf",10)返回123. 同样parseFloat()忽略字符串末尾的非数字字符。
Also if it's a user-entered value you should double-check that it actually is a number and perhaps provide an error message if it isn't.
此外，如果它是用户输入的值，您应该仔细检查它是否确实是一个数字，如果不是，可能会提供一条错误消息。
When you use the *, /or -operators JS tries to convert the string to a number automatically, so that's why those operators "work" (assuming the string canbe converted).
当您使用*,/或-运算符时，JS 会尝试自动将字符串转换为数字，这就是这些运算符“工作”的原因（假设字符串可以转换）。
回答by Kirill Ivlev
You should use the parseIntfunction and make sure the value is number(use isNaN function):
您应该使用该parseInt函数并确保该值为数字（使用 isNaN 函数）：
var val = $("#originalnum").val();
var num = 0;
if ( !isNaN(val) )
num= parseInt(val) + 1;
回答by DarkAjax
Use parseInt():
使用parseInt()：
var num= parseInt($("#originalnum").val(),10) + 1;
So your number is treated as an integer instead of a string (as .val()treats the result as string by default)
因此，您的数字被视为整数而不是字符串（.val()默认情况下将结果视为字符串）
