Material UI Select blurry placeholder along with value

Question

Below is my Select component. I am fetching some data and in useEffect setting categoryId. But the problem is that it's showing the placeholder in background like below .

import InputLabel from "@material-ui/core/InputLabel";
import MenuItem from "@material-ui/core/MenuItem";
import FormControl from "@material-ui/core/FormControl";
import Select from "@material-ui/core/Select";
import { categories } from "./categories";

export default function SimpleSelect() {
  const [categoryId, setCategoryId] = React.useState<number | null>(null);
  const subCategoryOptions = categories[2].children;

  useEffect(() => {
    setCategoryId(7);
  }, []);

  return (
    <div>
      <FormControl fullWidth>
        <InputLabel id="sub-category">Category</InputLabel>
        <Select
          labelId="sub-category"
          onChange={(e) => {
            setCategoryId(e.target.value as number);
          }}
          value={categoryId}
        >
          {subCategoryOptions.map((category) => {
            return (
              <MenuItem value={category.id} key={category.id}>
                {category.name}
              </MenuItem>
            );
          })}
        </Select>
      </FormControl>
    </div>
  );
}

codesandbox

Answer 1

In the console for your sandbox, I see the following warnings/errors:

Warning: `value` prop on `input` should not be null. Consider using an empty string to clear the component or `undefined` for uncontrolled components.
    in input (created by ForwardRef(SelectInput))
    in ForwardRef(SelectInput) (created by ForwardRef(InputBase))
    in div (created by ForwardRef(InputBase))
    in ForwardRef(InputBase) (created by WithStyles(ForwardRef(InputBase)))
    in WithStyles(ForwardRef(InputBase)) (created by ForwardRef(Input))
    in ForwardRef(Input) (created by WithStyles(ForwardRef(Input)))
    in WithStyles(ForwardRef(Input)) (created by ForwardRef(Select))
    in ForwardRef(Select) (created by WithStyles(ForwardRef(Select)))
    in WithStyles(ForwardRef(Select)) (at demo.tsx:20)
    in div (created by ForwardRef(FormControl))
    in ForwardRef(FormControl) (created by WithStyles(ForwardRef(FormControl)))
    in WithStyles(ForwardRef(FormControl)) (at demo.tsx:18)
    in div (at demo.tsx:17)
    in SimpleSelect (at index.tsx:6)
Material-UI: You have provided an out-of-range value `null` for the select component.
Consider providing a value that matches one of the available options or ''.
The available values are `7`, `8`, `9`, `10`, `11`, `12`. 
    in SelectInput (created by InputBase)
    in InputBase (created by WithStyles(ForwardRef(InputBase)))
    in WithStyles(ForwardRef(InputBase)) (created by Input)
    in Input (created by WithStyles(ForwardRef(Input)))
    in WithStyles(ForwardRef(Input)) (created by Select)
    in Select (created by WithStyles(ForwardRef(Select)))
    in WithStyles(ForwardRef(Select)) (at demo.tsx:20)
    in SimpleSelect (at index.tsx:6) 
Warning: A component is changing an uncontrolled input of type undefined to be controlled. Input elements should not switch from uncontrolled to controlled (or vice versa). Decide between using a controlled or uncontrolled input element for the lifetime of the component. More info: https://reactjs.org/docs/forms.html#controlled-components
    in input (created by ForwardRef(SelectInput))
    in ForwardRef(SelectInput) (created by ForwardRef(InputBase))
    in div (created by ForwardRef(InputBase))
    in ForwardRef(InputBase) (created by WithStyles(ForwardRef(InputBase)))
    in WithStyles(ForwardRef(InputBase)) (created by ForwardRef(Input))
    in ForwardRef(Input) (created by WithStyles(ForwardRef(Input)))
    in WithStyles(ForwardRef(Input)) (created by ForwardRef(Select))
    in ForwardRef(Select) (created by WithStyles(ForwardRef(Select)))
    in WithStyles(ForwardRef(Select)) (at demo.tsx:20)
    in div (created by ForwardRef(FormControl))
    in ForwardRef(FormControl) (created by WithStyles(ForwardRef(FormControl)))
    in WithStyles(ForwardRef(FormControl)) (at demo.tsx:18)
    in div (at demo.tsx:17)
    in SimpleSelect (at index.tsx:6)

If you address the issues by replacing null with empty string, it works fine:

import React, { useEffect } from "react";
import InputLabel from "@material-ui/core/InputLabel";
import MenuItem from "@material-ui/core/MenuItem";
import FormControl from "@material-ui/core/FormControl";
import Select from "@material-ui/core/Select";
import { categories } from "./categories";

export default function SimpleSelect() {
  const [categoryId, setCategoryId] = React.useState<number | "">("");
  const subCategoryOptions = categories[2].children;

  useEffect(() => {
    setCategoryId(7);
  }, []);

  return (
    <div>
      <FormControl fullWidth>
        <InputLabel id="sub-category">Category</InputLabel>
        <Select
          labelId="sub-category"
          onChange={(e) => {
            setCategoryId(e.target.value as number);
          }}
          value={categoryId}
        >
          {subCategoryOptions.map((category) => {
            return (
              <MenuItem value={category.id} key={category.id}>
                {category.name}
              </MenuItem>
            );
          })}
        </Select>
      </FormControl>
    </div>
  );
}