Javascript正则表达式匹配以数字结尾的字符串不一致

Question

我有以下正则表达式模式匹配所有以 URL 列表中的数字结尾的“行为”。

正则表达式 /\/ch(\d+)\/act(\d+)/gi

Javascript 代码

pageSrc[1] = "../ch01/index.html";
pageSrc[2] = "../ch01/act01/1.html";
pageSrc[3] = "../ch01/act01/2.html";
pageSrc[4] = "../ch01/act02/1.html";
pageSrc[5] = "../ch01/act02/2.html";
pageSrc[6] = "../ch01/actx/1.html";

var pattern = /\/ch(\d+)\/act(\d+)/gi;
for(var i=0; i<pageSrc.length; ++i){
  var hasAct = pattern.test(pageSrc[i]);
  console.log(hasAct);
}

预期结果与实际结果

|   String   | Expected Result |   Actual Result  |
| pageSrc[1] |       false     |     false        |
| pageSrc[2] |       true      |     true         |
| pageSrc[3] |       true      |     *FALSE       |
| pageSrc[4] |       true      |     true         |
| pageSrc[5] |       true      |     *FALSE       |
| pageSrc[6] |       false     |     false        |

我不确定为什么 pageSrc[3] 不会返回 true。我在 gskinner.com 上使用了 regEx 测试器，它工作正常，这里是链接 http://gskinner.com/RegExr/?344ap

谁能帮我看看？提前致谢!

Answer 1

删除 g 标志。来自 the RegExp.test documentation:

As with exec (or in combination with it), test called multiple times on the same global regular expression instance will advance past the previous match.

在重用这样的模式时，您不希望进行全局搜索。

> var pageSrc = [];
> pageSrc[1] = "../ch01/index.html";
  pageSrc[2] = "../ch01/act01/1.html";
  pageSrc[3] = "../ch01/act01/2.html";
  pageSrc[4] = "../ch01/act02/1.html";
  pageSrc[5] = "../ch01/act02/2.html";
  pageSrc[6] = "../ch01/actx/1.html";

  var pattern = /\/ch(\d+)\/act(\d+)/i;
  for(var i=0; i<pageSrc.length; ++i){
    var hasAct = pattern.test(pageSrc[i]);
    console.log(i, hasAct);
  }
  0 false
  1 false
  2 true
  3 true
  4 true
  5 true
  6 false