map function not working in React

Question

I am new to React JS, I was testing out some functions in fiddler. I am not sure why I get an error pointing to the map function. I am not able to render the array i defined.

Relevant snippet:

      {this.props.data.productSpecs.map(function(productSpec){
        <b>Category Name:</b> {productSpec};
      })}

Full code:

var productCategory = {
    productName: 'SamamgaTV1',
  productCategory: 'Television', 
  productSpecs: ['32inch','black','hd']
};

var ProductComponent = React.createClass({
  render: function() {
    return( <div>
                        <h2>Product</h2>
              <b>Product Name:</b> {this.props.data.productName}
              <h2>Category</h2>
              <b>Category Name:</b> {this.props.data.productCategory}
              <h2>Specs</h2>
              {this.props.data.productSpecs.map(function(productSpec){
                <b>Category Name:</b> {productSpec};
              })}
           </div>);
  }
});

ReactDOM.render(
  <ProductComponent data={productCategory} />,
  document.getElementById('container')
);

Steeve Pitis · Accepted Answer · 2016-10-12T13:28:14.523

43

First you missed to return, then you must return ONE element. Here you return a <p> and a TextNode

Moreover you need to provide a unique key.

Try with this :

{this.props.data.productSpecs.map(function(productSpec, i){
        return <span key={i}><b>Category Name:</b> {productSpec}</span>;
})}

edited Oct 12 '16 at 13:28

answered Oct 12 '16 at 13:21

Steeve Pitis

4,283
1
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24

Thanks.. this did the job... i dont think i need the key, but it helps when working with bigger applications, it shows how i can pass in IDs .. – floormind Oct 12 '16 at 13:28
2

I've just spent almost an hour before I realized I had forgotten the 'return' keyword... #rusty The key is needed to avoid a warning in the console and avoid a potential mess between items of the list – Jérôme Oudoul Jan 02 '20 at 15:05

Andreyco · Answer 2 · 2016-10-12T13:25:08.167

2

You need to return value from map handler.

{this.props.data.productSpecs.map(function(productSpec){
    return (<span><b>Category Name:</b> {productSpec}<span>);
})}

If you do not want to (or can't in some situations) wrap content in span, you can create & return fragment (very handy)

const createFragment = require('react-addons-create-fragment');

{this.props.data.productSpecs.map(function(productSpec){
    return createFragment({
        bold: <b>Category Name:</b>,
        spec: productSpec,
    });
})}

edited Oct 12 '16 at 13:25

answered Oct 12 '16 at 13:20

Andreyco

22,476
5
61
65

i tried that also, does not seem to work.. here is my jsfiddle linke https://jsfiddle.net/69z2wepo/59585/ – floormind Oct 12 '16 at 13:22
1

this fail because you are returning TWO elements. check my answer – Steeve Pitis Oct 12 '16 at 13:22
Yes, that's another issue which I overlooked. Updated the answer. – Andreyco Oct 12 '16 at 13:23

score 0 · Answer 3 · answered Nov 09 '18 at 04:07

0

It might be that you are using a string so you have to use the split method and pass in an empty string such as myValue.split('').map();

answered Nov 09 '18 at 04:07

Tyrone Moodley

3,442
1
15
16

map function not working in React

3 Answers3

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