打字稿:无法读取未定义的属性"toLowerCase" [英] Typescript: Cannot read property 'toLowerCase' of undefined

问题描述

我在网上遇到此错误:

 return filter ? value.filter(element => element.type.toLowerCase().indexOf(filter.toString().toLowerCase()) != -1) : value;

当element.type为空字符串(过滤空列)时.该如何解决?

when element.type is empty string (filtering empty column). How to fix this?

推荐答案

消息显示: element.type 是 undefined .在您的 filter 调用中添加对它的检查.像这样的事情，您的投入取决于您的期望，我只能对此进行猜测.

As the message states: element.type is undefined. Add a check on that in your filter call. Something like this, what you put depends on what you are expecting back and I can only guess at that.

return filter 
    ? value.filter(element => element.type && element.type.toLowerCase().indexOf(filter.toString().toLowerCase()) != -1) 
    : value;

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