javascript - 正则表达式验证字符的单次出现

Question

我想检查输入字符串以验证正确的文本。验证将使用 javascript 完成，现在我正在使用此代码:

keychar = String.fromCharCode(keynum);
var text = txtBox.value + keychar;
textcheck = /(?!.*(.)\1{1})^[fenFN,]*$/;
return textcheck.test(text);

允许的字符串例如:
f
电子
f,e
n,f,e,F,N

不允许的例子:
好
铁
f,f
f,ee
f,e,n,f
n,,(虽然这可能没问题)

这可以用 Javascript 中的正则表达式解决吗？

Answer 1

虽然可以使用正则表达式，但它会产生一个相当大的正则表达式，可能难以理解(因此难以维护)。我会按照 Benjam 的建议选择“手动”选项。

然而，使用正则表达式，您可以这样做:

var tests = [
  'f',
  'e',
  'f,e',
  'n,f,e,F,N',
  'ff',
  'fe',
  'f,f',
  'f,ee',
  'f,e,n,f',
  'n,,',
  'f,e,e'
];

for(var i = 0; i < tests.length; i++) {
  var t = tests[i];
  print(t + ' -> ' + (t.match(/^([a-zA-Z])(?!.*\1)(,([a-zA-Z])(?!.*\3))*$/) ? 'pass' : 'fail'));
}

将打印:

f -> pass
e -> pass
f,e -> pass
n,f,e,F,N -> pass
ff -> fail
fe -> fail
f,f -> fail
f,ee -> fail
f,e,n,f -> fail
n,, -> fail
f,e,e -> fail

正如您在 Ideone 上看到的那样.

一个小的解释:

^                     # match the start of the input
([a-zA-Z])            # match a single ascii letter and store it in group 1
(?!.*\1)              # make sure there's no character ahead of it that matches what is inside group 1
(                     # open group 2
  ,([a-zA-Z])(?!.*\3) #   match a comma followed by a single ascii letter (in group 3) that is not repeated
)*                    # close group 2 and repeat it zero or more times
$                     # match the endof the input