Rendering React Components from Array of Objects

Rendering React Components from Array of Objects

I have some data called stations which is an array containing objects.
stations : [
{call:’station one’,frequency:’000′},
{call:’station two’,frequency:’001′}
]

I’d like to render a ui component for each array position. So far I can write
var stationsArr = []
for (var i = 0; i < this.data.stations.length; i++) { stationsArr.push(

{this.data}

)
}

And then render
render(){
return (
{stationsArr}
)
}

The problem is I’m getting all of the data printing out. I instead want to just show a key like {this.data.call} but that prints nothing.
How can I loop through this data and return a new UI element for each position of the array?

Solutions/Answers:

Solution 1:

You can map the list of stations to ReactElements.

With React >= 16, it is possible to return multiple elements from the same component without needing an extra html element wrapper. Since 16.2, there is a new syntax <> to create fragments. If this does not work or is not supported by your IDE, you can use <React.Fragment> instead. Between 16.0 and 16.2, you can use a very simple polyfill for fragments.

Related:  Inverse of [].filter in JS?

Try the following

// Modern syntax >= React 16.2.0
const Test = ({stations}) => (
  <>
    {stations.map(station => (
      <div className="station" key={station.call}>{station.call}</div>
    ))}
  </>
); 

// Modern syntax < React 16.2.0
// You need to wrap in an extra element like div here

const Test = ({stations}) => (
  <div>
    {stations.map(station => (
      <div className="station" key={station.call}>{station.call}</div>
    ))}
  </div>
); 

// old syntax
var Test = React.createClass({
    render: function() {
        var stationComponents = this.props.stations.map(function(station) {
            return <div className="station" key={station.call}>{station.call}</div>;
        });
        return <div>{stationComponents}</div>;
    }
});

var stations = [
  {call:'station one',frequency:'000'},
  {call:'station two',frequency:'001'}
]; 

ReactDOM.render(
  <div>
    <Test stations={stations} />
  </div>,
  document.getElementById('container')
);

Don’t forget the key attribute!

https://jsfiddle.net/69z2wepo/14377/

Solution 2:

I have an answer that might be a bit less confusing for newbies like myself. You can just use map within the components render method.

render () {
   return (
       <div>
           {stations.map(station => <div> {station} </div>)} 
       </div>
   );
}

Solution 3:

this.data presumably contains all the data, so you would need to do something like this:

var stations = [];
var stationData = this.data.stations;

for (var i = 0; i < stationData.length; i++) {
    stations.push(
        <div key={stationData[i].call} className="station">
            Call: {stationData[i].call}, Freq: {stationData[i].frequency}
        </div>
    )
}

render() {
  return (
    <div className="stations">{stations}</div>
  )
}

Or you can use map and arrow functions if you’re using ES6:

const stations = this.data.stations.map(station =>
    <div key={station.call} className="station">
      Call: {station.call}, Freq: {station.frequency}
    </div>
);