javascript - Handlebars /功能最终处于不可能的状态

Question

我有以下 Handlebars 助手，在 typescript 文件中定义。

当助手输入字符串 "test" 时，且 maxResidualLength 为 10 ，尽管检查员告诉我clippedString.length > maxResidualLength，调试器语句仍然被命中。等于 false

    Handlebars.registerHelper("ClipYearsFromString", function (strg: string, maxResidualLength:number) {
        var pattern = /(\b\d{4}.\b|\b\d{4}\b)/g; //remove sets of four digits or four digits with a non alpha character behind them.

        var clippedString = strg.replace(pattern, "");

        if (typeof (maxResidualLength) == "number" && maxResidualLength > 0) 
        {
            if (clippedString.length > maxResidualLength);
            {
                debugger;
                clippedString = clippedString.substr(0, maxResidualLength) + "…";
            }
        }
        return clippedString;
    });

在模板中调用助手如下:

   <span>{{{ClipYearsFromString SelectedRankingPool.PoolName 10}}}</span>

SelectedRankingPool.PoolName始终是一个字符串。

这是怎么发生的？所有主要浏览器都会出现相同的行为，无论是 Chrome、Firefox 还是 IE，如果我在 typescript 和 Handlebars 之外进行帮助程序注册，这种情况仍然会发生。

function derp(strg, maxResidualLength)
    {
      var pattern = /(\b\d{4}.\b|\b\d{4}\b)/g;   
      var clippedString = strg.replace(pattern, "");
      if (typeof (maxResidualLength) == "number" && maxResidualLength > 0) 
            {
                if (clippedString.length > maxResidualLength);
                {
                    debugger;
                    clippedString = clippedString.substr(0, maxResidualLength) + "…";
                }
            }
            return clippedString;
    }

    console.log(derp("test", 10)); //hits debugger

Answer 1

这是一件令人讨厌的小事。我在一个奇怪的地方看到一个 ;:

if (clippedString.length > maxResidualLength); // <-- weird?

简单再现示例:

if(false); // ";" terminates the if statement.
{
    alert('I get executed anyway...');
}