TypeError: Cannot read properties of undefined (reading 'includes')

Question

TypeError: Cannot read properties of undefined (reading 'includes'). I got this mistake, but I can't get through and solve the problem. Error shows this line

     {addOption && addOption.length && (
                      <Select
                        onClick={(e) => e.stopPropagation()}
                        labelId="demo-customized-select-label"
                        id="demo-customized-select"
                        // value={addOption[i]}
                        value={addOption[i]}
                        multiple
                        onChange={(ev) => handleadd(ev, i)}
                        renderValue={() => {
                          return selectedOptionNames[i];
                        }}
                        input={<BootstrapInput />}
                      >
                        <MenuItem value={1} disabled>
                          FILE
                        </MenuItem>
                        <MenuItem value={2}>
                          <Checkbox checked={addOption[i].includes(2)} />
                          <ListItemText>{addOptionNames[1]}</ListItemText>
                        </MenuItem>
                        <MenuItem value={3}>
                          <Checkbox checked={addOption[i].includes(3)} />
                          <ListItemText>{addOptionNames[2]}</ListItemText>
                        </MenuItem>
                        <MenuItem value={4}>
                          <Checkbox checked={addOption[i].includes(4)} />
                          <ListItemText>{addOptionNames[3]}</ListItemText>
                        </MenuItem>
                      </Select>

Answer 1

As per your code snippet addOption is an array. So, you should have to perform the includes method on the array itself, not on a single array element. Check this out in your Menu Items :

<MenuItem value={X}>
   <Checkbox checked = { addOption.includes(X) } />
   <ListItemText> { addOptionNames[X-1] } </ListItemText>
</MenuItem>