新人菜鸟求解一个js问题

function nameCheck(){
                var uname =document.getElementById("uname");
                var span =document.getElementById("uname_span");
                if(uname=null||uname==""){
                    span.innerText="错误输入";
                    return false;
                }else{
                    span.innerText="正确输入";
                    return true;
                }
                        
            }