Can anyone reply why key is having a prefix of undefined ?

[bshivam1]

{
autofocus: false,
input: true,
tableView: true,
inputType: "text",
inputMask: "",
label: "Text",
key: "undefinedText", // <-This one
placeholder: "",
prefix: "",
suffix: "",
multiple: false,
defaultValue: "",
protected: false,
unique: false,
persistent: true,
hidden: false,
clearOnHide: true,
spellcheck: true,
+validate: {...},
+conditional: {...},
type: "textfield",
$$hashKey: "object:902",
labelPosition: "top",
inputFormat: "plain",
+tags: [...],
+properties: {...}
},

• {
  autofocus: false,
  input: true,
  tableView: true,
  inputType: "number",
  label: "Number",
  key: "undefinedNumber", // <-This one
  placeholder: "",
  prefix: "",
  suffix: "",
  defaultValue: "",
  protected: false,
  persistent: true,
  hidden: false,
  clearOnHide: true,
  +validate: {...},
  type: "number",
  $$hashKey: "object:1017",
  labelPosition: "top",
  +tags: [...],
  +conditional: {...},
  +properties: {...}
  @travist