Cannot read property 'length' of null in javascript for loop

Question

I'm trying to make a markdown editor like Stack Overflow has. I get this error listed in the title if I don't actually type an asterisk AND a http:// containing phrase into the textarea. If I only type an asterisk containing phrase, the error refers to this line: `if(linkify.length!==0)` Here's a jsfiddle to show you what I mean. Here's my HTML: ```

``` Here's my JS: ``` var val=$('textarea').val(), boldify = val.match(/\*\*[A-Za-z0-9]+\*\*/gim), italicify = val.match(/\*[A-Za-z0-9]+\*/gim),linkify = val.match(/http\:\/\/[A-z0-9]+\.[A-z0-9]+/gim); $(document.body).on('click', 'button', function() { val=$('textarea').val(), boldify = val.match(/\*\*[A-Za-z0-9]+\*\*/gim), italicify = val.match(/\*[A-Za-z0-9]+\*/gim),linkify = val.match(/http\:\/\/[A-z0-9]+\.[A-z0-9]+/gim); if (boldify.length!== 0){ for (var i=0; i < boldify.length; i++) { var boldMatch= boldify[i], boldReplace = boldMatch.replace(/\*\*[A-z0-9]+\…

Accepted Answer

instead of using `match` function which returns a null if the string doesnt match the provided regex use the `test` function which returns a true/false and then if you need it you can use the `match` function.

basically you are performing `null.length` which is obviously invalid as the `match` is returning you a null

or you could just perform a `null` check before you check for the length and just do the regex matching once.

```
if(linkify!==null && linkify.length!== 0)
{
  //do smthing
}
```

Cannot read property 'length' of null in javascript for loop

Solution

Problem