A simple JavaScript If query. If one "if" is used I don't want the others to be used. If I type 18 the following answers from the other ifs show up : 



var age = prompt("please enter your age")
          
var letters = /^[A-Za-z]+$/;
              
                   
            
                if (age== 18) {
                    alert("welcome to our website")
                    
                   
                 }
                 if (age > 18) {
                    alert("welcome to our website") 
                    
                 } 
                 if (age < 18) {
                    alert("you aren't allowed to visit this website")
                    window.close()
                 }
                 if (age= letters){
                   alert("please enter a valid number")
                   prompt("please enter your age")
                 }