如何将regex表达式用于验证介于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，但它并不是精确的。

表达式I使用:/^1-4{0，1}(？：.d{1，2})？$/

要求只接受1.0到4.5之间的值

但

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})?$/**),
        ],
      ],
    });
  }

目前将数字限制在1.0到4.0之间，但问题出现在小数点上，如果在小数位中输入任何介于6-9之间的数字，如1.7、2.8、3.9，则会显示错误。

验收标准为1.0至4.5。

​

​

这个图像显示值被输入到多个十进制位，这是错误的，

只需要一个小数位值。

Answer 1

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

解释

/^[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.

Answer 2

Regex很难检查数字范围。它应该考虑非十进制数吗？如果有一个以上的小数点呢？如果你想增加/减少范围怎么办？下面是关于这个主题的更多信息：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否低于或高于标准，例如，允许您适当地显示自定义错误消息。而regex将简单地计算为true/false。

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

Answer 3

您可以使用以下regex模式：

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

​

Demo

​

这个正则表达式表示匹配：

^                            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