React JSX: rendering nested arrays of objects

Question

I have a component with the following render:

  render() {
    const { policy } = this.props;
    let deployment = policy.Deployment;
    let value = policy.value;
    let policyLegend = deployment.policyLegend;
    let policyObj = this.valueToPolicy(policyLegend, value);
    console.log(policy);
    console.log(deployment);
    console.log(value);
    console.log(policyLegend);
    console.log(policyObj);
    return(
      <div>
        <Form onSubmit={ (event) => this.handleSubmit(event, this.props) }>
          {
            policyLegend.map(function(policy) {
              <div>
                <h3 key={ policy.id }>{ policy.displayName }</h3>
                {
                  policy.values.map(value => {
                    return(
                      <Form.Field key={ value.name }>
                        <label>{ value.displayName }</label>
                        <Checkbox toggle />
                      </Form.Field>
                    );
                  })
                }
              </div>
            })
          }
          <Button name={ 'Submit' } type='submit'>Submit</Button>
          <Button onClick={ this.props.onCancel }>Cancel</Button>
        </Form>
      </div>
    )
  }

<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react-dom.min.js"></script>

policyLegend is an array of objects with a 'values' array inside each object.

When my application builds, I receive no errors but nothing appears on my component page. I'm not sure where I'm going wrong and would appreciate any advice, thank you.

score 4 · Accepted Answer · answered Nov 29 '17 at 18:06

It's because you do not return anything inside the policyLegend map. Try this:

{
    policyLegend.map((policy) => {
        return (
            <div>
                <h3 key={ policy.id }>{ policy.displayName }</h3>
                {
                    policy.values.map(value => {
                        return(
                            <Form.Field key={ value.name }>
                                <label>{ value.displayName }</label>
                                <Checkbox toggle />
                            </Form.Field>
                        );
                    })
                }
            </div>
        );
    })
}

score 3 · Answer 2 · answered Nov 29 '17 at 18:07

You are not returning the JSX from your map method. Once you return the JSX you formed :

policyLegend.map(function(policy) {
              return (<div>
                <h3 key={ policy.id }>{ policy.displayName }</h3>
                {
                  policy.values.map(value => {
                    return(
                      <Form.Field key={ value.name }>
                        <label>{ value.displayName }</label>
                        <Checkbox toggle />
                      </Form.Field>
                    );
                  })
                }
              </div>)
            })

You should get the result you're looking for

hi, why can't I do `return policyLegend.map(.... => (...) )` ? what would that return do? — MMMM, Jun 25 '19 at 21:08

React JSX: rendering nested arrays of objects

2 Answers2

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