RegExp with variables and .Test()

Question

This is possibly a duplicate but I just cant figure out what is wrong with this regular expression.

<p id="demo">Result comes here:</p>
<button onclick="myFunction()">Check</button>

<script>
function myFunction()
{
    var str = "The best things in life are free";
    var sTerm="things";
    var regXSearch= "/\\b"+sTerm+"/gi";
    var regX = new RegExp(regXSearch);
    //var regX= new RegExp(/\bthings/gi);
    var result = regX.test(str);

    document.getElementById("demo").innerHTML=result;
}
</script>

For some reason this returns false. If I check the value of the regXSearch variable it will be exacly the same as what is in the regX RegExp that is commented out. And that is in fact returning true.

Scott Sauyet · Accepted Answer · 2014-04-14 20:32:11Z

2

You're combining the two different regex syntaxes. Try this:

var regXSearch= "\\b"+sTerm;
var regX = new RegExp(regXSearch, "gi");

You can use regex literals such as

/\bthings/gi

or you can use the RegExp constructor function like this:

new RegExp("\\bthings", "gi")

Although I can see no good reason to do so, you could also even do

new RegExp(/\bthings/gi)

But yours is an illegal mix of these:

new RegExp("/\\bthings/gi");  // DON'T DO THIS!  :-)

edited Apr 14, 2014 at 20:32

answered Apr 14, 2014 at 20:25

Scott Sauyet

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1 Comment

JSking Over a year ago

how do I then use variable as the hambugger here: > db.restaurants.find( { cuisine: /Hamburgers/ } ).count()

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