Tengo 4 selecciones y estoy tratando de obtener el dispositivo y el teléfono o el reloj y el modelo del dispositivo y finalmente el problema con el dispositivo, por lo que todo funciona hasta que elijo el dispositivo y luego el teléfono, pero cuando trato de elegir el modelo del teléfono no hay valores, no pude descifrarlo, este es mi código.

 var subjectObject = { Phone: { Samsung: { A50: [ "Screen", "Screen High Copy", "Battery", "Charging Port", "Speaker", "Front Camera", "Back Camera", "Home Button", "Loud Speaker", "IC Brightness", "IC Charging", "IC Display", "IC Touch", "IC WI-FI", "IC Baseband", "Short Circuit", ], A70: [ "Screen", "Screen High Copy", "Battery", "Charging Port", "Speaker", "Front Camera", "Back Camera", "Home Button", "Loud Speaker", "IC Brightness", "IC Charging", "IC Display", "IC Touch", "IC WI-FI", "IC Baseband", "Short Circuit", ], }, Watch: { Apple: { SmartWatch1: ["Broken Screen"], }, }, }; window.onload = function () { var device = document.getElementById("device"); var phone = document.getElementById("phone"); var model = document.getElementById("model"); var problem = document.getElementById("problem"); for (var x in subjectObject) { device.options[device.options.length] = new Option(x, x); } device.onchange = function () { phone.length = 1; model.length = 1; problem.length = 1; //display correct values for (var y in subjectObject[this.value]) { phone.options[phone.options.length] = new Option(y, y); } }; phone.onchange = function () { model.length = 1; //display correct values var z = subjectObject[phone.value][this.value]; for (var i = 0; i < z.length; i++) { model.options[model.options.length] = new Option(z[i], z[i]); } }; model.onchange = function () { problem.length = 1; //display correct values var z = subjectObject[model.value][this.value]; for (var i = 0; i < z.length; i++) { problem.options[problem.options.length] = new Option(z[i], z[i]); } }; };