How to render react components by using map and join?

Question

I have one component which is going to display Array of String. The code looks like this:

React.createClass({
  render() {
     

        this.props         


        
                      

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Answer 1

If I just want to render a comma-separated array of components, I usually find reduce too verbose. A shorter solution in such cases is

{arr.map((item, index) => (
  <Fragment key={item.id}>
    {index > 0 && ', '}
    <Item {...item} />
  </Fragment>
))}

{index > 0 && ', '} will render a comma followed by a space in front of all array items except the first one.

If you want to separate the second-to-last item and the last one by something else, say the string ' and ', you can replace {index > 0 && ', '} with

{index > 0 && index !== arr.length - 1 && ', '}
{index === arr.length - 1 && ' and '}

Answer 2

Use nested array to keep "," outside.

  <div>
      {this.props.data.map((element, index) => index == this.props.data.length - 1 ? <span key={index}>{element}</span> : [<span key={index}>{element}</span>, ", "])}
  </div>

Optimize it by saving the data to array and modify last element instead of checking if its last element all the time.

  let processedData = this.props.data.map((element, index) => [<span key={index}>{element}</span>, ", "])
  processedData [this.props.data.length - 1].pop()
  <div>
      {processedData}
  </div>