javascript use test with regex for letters, numbers, spaces and dash

I use a javascript test with regex for numbers, letters and underscore. I want to change the regex to regex for letters, numbers, spaces and dash. But how? ``` re = /^\w+$/; if(!re.test(form.username.value)) { alert("Username must contain only letters, numbers and underscores. Please try again"); form.username.focus(); return false; } ```