Question: I'm trying to detect an occurrence of a string within string. But the code below always returns "null". Obviously something went wrong, but since I'm a newbie, I can't spot it. I'm expecting that the code returns "true" instead of "null"

```
var searchStr = 'width'; 
var strRegExPattern = '/'+searchStr+'\b/'; 
"32:width: 900px;".match(new RegExp(strRegExPattern,'g'));

```

Answer: 
Please don't put '/' when you pass string in RegExp option

Following would be fine

```
var strRegExPattern = '\\b'+searchStr+'\\b'; 
"32:width: 900px;".match(new RegExp(strRegExPattern,'g'));

```
The right tool for this job is not regex, but String.indexOf: 

```
var str = '32:width: 900px;',
    search = 'width',
    isInString = !(str.indexOf(search) == -1); 

// isInString will be a boolean. true in this case

```

Documentation: <https://developer.mozilla.org/en/Core_JavaScript_1.5_Reference/Objects/String/indexOf>