javascript - ReactJs: How to handle empty array with map function inside render method - Stack Overflow

admin管理员组

文章数量:1420228

I m trying to print table with some JSON data, but I am not able to render empty array when I am using map method.

JSON DATA :

    [{
	"id": 6,
	"firstname": "Sharon",
	"lastname": "Jenkins",
	"specialties": []
}, {
	"id": 2,
	"firstname": "Helen",
	"lastname": "Leary",
	"specialties": [{
		"id": 1,
		"name": "radiology"
	}]
}, {
	"id": 4,
	"firstname": "Rafael",
	"lastname": "Ortega",
	"specialties": [{
		"id": 2,
		"name": "surgery"
	}]
}, {
	"id": 5,
	"firstname": "Henry",
	"lastname": "Stevens",
	"specialties": [{
		"id": 1,
		"name": "radiology"
	}]
}]

I m trying to print table with some JSON data, but I am not able to render empty array when I am using map method.

JSON DATA :

    [{
	"id": 6,
	"firstname": "Sharon",
	"lastname": "Jenkins",
	"specialties": []
}, {
	"id": 2,
	"firstname": "Helen",
	"lastname": "Leary",
	"specialties": [{
		"id": 1,
		"name": "radiology"
	}]
}, {
	"id": 4,
	"firstname": "Rafael",
	"lastname": "Ortega",
	"specialties": [{
		"id": 2,
		"name": "surgery"
	}]
}, {
	"id": 5,
	"firstname": "Henry",
	"lastname": "Stevens",
	"specialties": [{
		"id": 1,
		"name": "radiology"
	}]
}]

My Code :

 {this.state.vets.map(vet =><tr><td>{vet.firstname}</td>
                  {  
                                  
                  vet.specialties.map((subitem,i) => {
                       
                    return <td>{subitem.name}</td> })}<td>EDIT</td><td id={vet.firstname}><div class="funkyradio">

Now I am getting the following error

As Sharon doesn't have a specialist, I need to print as N/A.

How can I check the specialities are empty and print N/A.

• javascript
• reactjs
• html

Share Improve this question Follow edited Feb 26, 2019 at 10:26 Egon Allison 1,39611 gold badge1414 silver badges2222 bronze badges asked Feb 26, 2019 at 7:45 Srikanthreddy KothaSrikanthreddy Kotha 5522 silver badges44 bronze badges 1

• This is happening because the specialities array of your first object is empty so the second map function does not iterate over that field. – Atin Singh Commented Feb 26, 2019 at 7:53

Add a ment  | 

4 Answers 4

Sorted by: Reset to default 2

use conditional statment like this

{ this.state.vets.length > 0 
 ? this.state.vets.map(()=>Your logic)
 : <Your custom message/>
}

try rendering always the TD tag, like:

{
  this.state.vets.map(vet =>
    <tr>
      <td>{vet.firstname}</td>
        <td>                
          {vet.specialties.map((subitem,i) => {
            return <span>{subitem.name}</span>
          })}
        </td>
        <td>EDIT</td>
        <td id={vet.firstname}>
          <div class="funkyradio">

<table>
        {dataJSON.map(({ id, firstname, lastname, specialties }) => {
          return (
            <tr>
              <td> {`${firstname} ${lastname}`} </td>
              <td> {specialties.map(specialty => specialty.name).join(",")} </td>
              <td> <span> EDIT </span> </td>
            </tr>
          );
        })}
</table>

Mainly for readability, instead of using the object property, I would create a separate function that will return the specialties, if any, otherwise N/A

本文标签： javascriptReactJs How to handle empty array with map function inside render methodStack Overflow