如何使用正则表达式来验证 1.0 到 4.5 之间的数字（十进制值之间的范围）？

Question

我需要一个表达式来验证 1.0 到 4.5 之间的数字，但它不能准确地工作。

我使用的表达式：/^[1-4]{0,1}(?:[.]\d{1,2})?$/

要求只接受 1.0 到 4.5 之间的值

但是

buildInserForm(): void {
    this.insertLeavesForm = this.fb.group({
     **your text**
      hours: [
        { value: 4.5, disabled: true },
        [
          Validators.required,
          Validators.pattern(**/^[1-4]{0,1}(?:[.]\d{1,2})?$/**),
        ],
      ],
    });
  }

目前限制数字从1.0到4.0，但问题出在小数点，如果输入小数点后6-9之间的任何数字，如1.7、2.8、3.9，都会显示错误。

验收标准为 1.0 到 4.5。

此图显示输入的值有多个小数位，这是错误的，
只需要一位小数。

Answer 1

您可以使用以下正则表达式模式：

^(?:[1-3](?:\.\d{1,2})?|4(?:\.(?:[0-4][0-9]|50?)?))$

Demo

这个正则表达式匹配：

^                            start of the input
(?:
    [1-3]                    match 1-3
    (?:\.\d{1,2})?           followed by optional decimal and 1 or 2 digits
    |                        OR
    4                        match 4
    (?:
        \.                   decimal point
        (?:[0-4][0-9]|50?)?  match 4.00 to 4.49 or 4.5 or 4.50
    )
)
$                            end of the input

Answer 2

正则表达式很难检查数字范围。它应该考虑非十进制数吗？如果多于一位小数怎么办？如果您想要 increase/decrease 范围怎么办？以下是关于该主题的更多信息：Regular expression Range with decimal 0.1 - 7.0

我建议使用简单的 min/max 验证器。此外，这还可以让您控制用户值是低于还是高于标准，例如，让您适当地显示自定义错误消息。而正则表达式将简单地评估为 true/false.

[
 Validators.required,
 Validators.min(1),
 Validators.max(4.5),
 Validators.maxLength(3)
]

Answer 3

这是我创建的正则表达式。 模式(/^[1-3]{0,1}(?:[.][0-9]{0,1})?[4]{0,1}(?:[. ][0-5]{0,1})?$/)

说明

/^[1-3]{0,1}(?:[.][0-9]{0,1})?[4]{0,1}(?:[.][0-5]{0,1})?$/


/^            start of the input
[1-3]         First input to be taken between
{0,1}         This shows how many times it can be repeated
(             Parenthesis shows next entered digit is optional
?             Question mark is for using digit zero or once
:[.]          This is for what the next Character would be eg ".", "@"
[0-9]         input to be taken between.
{0,1}         This shows how many times it can be repeated.
)             Option part closes
?             Question mark is for using digit zero or once.
[4]           This shows what can be other input that can be taken
{0,1}         How many times it can be use , SO in this case 0 or 1 times


(?:[.]       There after again same option part  with decimal point

             decimal value of 4and its limitation for 0 to 5
[0-5]        This is to set limitation 0-5 as per our requirement
{0,1}        Its existence 0 or 1 times
)            Close of optional part.
?            Thereafter showing the existence of an optional part once or twice.
$/           Shows to match expression after it.

如何使用正则表达式来验证 1.0 到 4.5 之间的数字（十进制值之间的范围）？

How to put regex expression to validate number between 1.0 to 4.5 (range between decimal values)?

javascript

regex

validation

typescript

angular

Demo