Question

当字符串包含一个精确的子字符串例如2次时，我需要一个正则表达式。所以

asdgsadg hello asdadsg hello dasadg将是真的

asdgsadg hello asdadsg hello dasadg hello将是假的

子字符串为hello

时

不幸的是，我无法/hello/g并计算长度...

谢谢！

Answer 1

正则表达式是：

/^(?!(.*hello){N+1})(.*hello){N}.*$/

'N+1' = 3和'N' = 2，如果您想准确地允许2 hello。

See demo

Answer 2

这就是工作：

/^(?:(?!\bhello\b).)*(?:\bhello\b(?:(?!\bhello\b).)*){2}$/

＆＃13;

var test = [
    'asdadsg hello dasadg',
    'asdgsadg hello asdadsg hello dasadg',
    'asdgsadg hello asdadsg hello dasadg hello',
];
console.log(test.map(function (a) {
  return a+' :'+/^(?:(?!\bhello\b).)*(?:\bhello\b(?:(?!\bhello\b).)*){2}$/.test(a);
}));

＆＃13;

<强>解释

/
  ^
  (?:                   : non capture group
    (?!\bhello\b).      : asserts there is not hello, followed by a character
  )*                    : group repeated 0 or more times
  (?:                   : non capture group
    \bhello\b           : hello
    (?:                 : non capture group
      (?!\bhello\b).    : asserts there is not hello, followed by a character
    )*                  : group repeated 0 or more times
  ){2}                  : group repeated twice
  $
/

Answer 3

这是我迄今为止找到的最简单的解决方案 <svg> <defs> <pattern id="wood" patternUnits="userSpaceOnUse" width="240" height="300" > <image xlink:href="http://hd.wallpaperswide.com/thumbs/girl_beach_background-t2.jpg" width="400" height="400" /> </pattern> </defs> <text y="2em">Nice Beach</text><text y="3em">Isnt't It</text> </svg> Run code snippet

正则表达式：精确包含n次字符串

3 个答案: