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How to get first N number of elements from an array

Posted by: admin November 30, 2017 Leave a comment

Questions:

I am working with Javascript(ES6) /FaceBook react and trying to get the first 3 elements of an array that varies in size. I would like do the equivalent of Linq take(n).

In my Jsx file I have the following:

var items = list.map(i => {
  return (
    <myview item={i} key={i.id} />
  );
});

Then to get the first 3 items I tried

  var map = new Map(list);
    map.size = 3;
    var items = map(i => {
      return (<SpotlightLandingGlobalInboxItem item={i} key={i.id} />);
    });

This didn’t work as map doesn’t have a set function.

Can you please help?

Answers:

I believe what you’re looking for is:

// ...inside the render() function

var size = 3;
var items = list.slice(0, size).map(i => {
    return <myview item={i} key={i.id} />
}

return (
  <div>
    {items}
  </div>   
)

Questions:
Answers:

To get the first n elements of an array, use

array.slice(0, n);

Questions:
Answers:

Do not try doing that using a map function. Map function should be used to map values from one thing to other. When the number of input and output match.

In this case use filter function which is also available on the array. Filter function is used when you want to selectively take values maching certain criteria. Then you can write your code like

var items = list
             .filter((i, index) => (index < 3))
             .map((i, index) => {
                   return (
                     <myview item={i} key={i.id} />
                   );
              });