Check validate webaddress using javascript reg expression

web = 'your web address';
var aweb = ignoreSpaces(web);
var filterweb = /^([A-Za-z0-9_\-\.])+([A-Za-z0-9_\-\.]{2,4})+\.([A-Za-z]{2,4})$/;
if(filterweb.test(aweb)){
        alert('correct')
    }
    else{
       alert('incorrect')
    }
try this for javascript