嵌套渲染不影响DOM

Question

Used: formik

I am rendering input fields for a form based on data from an external array. The structure of this data is as follows:

 {
    label: 'Test Question,
    value: 'testquestion',
    type: 'select',
    options: [{ label: 'yes', value: 'true' }, { label: 'no', value: 'false' }],
    conditionalFields: [
      {
        condition: {
          conditionalQuestion: 'experiencePhotography',
          answer: 'true',
          questions: [
            {
              label: 'Test Question ADDED IF YES',
              value: 'testQuestionYES',
              type: 'text'
            }
          ]
        }
      }
    ]
  }

and I am rendering it as follows:

case 'select': {
            return (
              <Fragment key={formField.value}>
                <Select name={formField.value} placeholder={formField.label}>
                  {formField.options &&
                    formField.options.map(option => (
                      <Select.Option key={option.value} name={option.value}>
                        {option.label}
                      </Select.Option>
                    ))}
                </Select>
                {formField.conditionalFields &&
                  formField.conditionalFields.length > 0 &&
                  formField.conditionalFields.forEach(conditionalField => {
                    if (values[formField.value]) {
                      if (values[formField.value] === conditionalField.condition.answer) {
                        conditionalField.condition.questions.forEach(question => {
                          console.log(question);
                          return (
                            <Fragment>
                              <Field
                                key={question.value}
                                name={question.value}
                                render={({ field }) => <CustomInput {...field} type="text" label={question.label} />}
                              />
                            </Fragment>
                          );
                        });
                      }
                    }
                  })}
              </Fragment>
            );
          }

So in this case, a element Select is rendered, with the relevant options. However, since the provided data has a 'conditionalFields' field, I can check the value of the selected dropdown item (done through Formik).

values[formField.value] gets data from Formik.

The data is there, and console.log(question) outputs data, but the Field element below that isn't returned or shown on the DOM.

Answer 1

forEach returns undefined , so you won't render anything when you use {formField.conditionalFields.forEach(/*...*/} (which is what you're doing if we remove the two guards there).

Looking inside your forEach , it looks like you'll want filter and then map , eg:

{ formField.conditionalFields &&
  formField.conditionalFields.length > 0 &&
  values[formField.value] &&
  formField.conditionalFields
    .filter(conditionalField => values[formField.value] === conditionalField.condition.answer)
    .map(conditionalField => conditionalField.condition.questions.map(question => {
      return (
        <Fragment>
          <Field
            key={question.value}
            name={question.value}
            render={({ field }) => <CustomInput {...field} type="text" label={question.label} />}
          />
        </Fragment>
      );
    }))
}

...or along those lines.

FWIW, you can use destructuring in the filter parameter, and there's no need for a Fragment around a single element (the Field ):

{ formField.conditionalFields &&
  formField.conditionalFields.length > 0 &&
  values[formField.value] &&
  formField.conditionalFields
    .filter(({condition: {answer}}) => values[formField.value] === answer)
    .map(conditionalField => conditionalField.condition.questions.map(question => (
      <Field
        key={question.value}
        name={question.value}
        render={({ field }) => <CustomInput {...field} type="text" label={question.label} />}
      />
    )))
}