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JavaScript React Basics (2018) Introducing Props Iterating and Rendering with map()

yoav green
yoav green
8,611 Points
Posted by yoav green
yoav green
8,611 Points

i'm keep getting a message in the console

react.development.js:316 Warning: Each child in an array or iterator should have a unique "key" prop.

Check the render method of App. See https://fb.me/react-warning-keys for more information. in Player (created by App) in App

1 Answer

Cheo R
Cheo R
37,150 Points
Cheo R
Cheo R
37,150 Points

The key prop's just react's way to keep track of elements when iterating over them.

You can use the element's index (from the array it's in), but since items can be added/removed from a list, it's better to use something more unique. The key's are for react's internal use. 

const food = ['tacos', 'salsa', 'tamarindo', 'torta'];

  <ul>
    {
      food.map((item, index) => <Food key={item.name} obj={item}>);
    }
  </ul>

Where you can replace item.name with index.