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'));

```
Notice that '\\b' is a single slash in a string followed by the letter 'b', '\b' is the escape code `\b`, which doesn't exist, and collapses to 'b'.

Also consider escaping metacharacters in the string if you intend them to only match their literal values.

```
var string = 'width';
var quotemeta_string = string.replace(/[^$\[\]+*?.(){}\\|]/g, '\\$1'); // escape meta chars
var pattern = quotemeta_string + '\\b';
var re = new RegExp(pattern);
var bool_match = re.test(input); // just test whether matches
var list_matches = input.match(re); // get captured results

```