Javascript es6 array mapping

Question

I need help creating a function that gonna return me 3 elements from an array each time with time interval of 3 seconds. Let say I have an array

const Array = [{name:'A'},{name:'B'},{name:'C'},{name:'D'},{name:'E'},{name:'F'},{name:'G'},{name:'H'},{name:'I'}];

It should return array like

 [{name:'A'},{name:'B'},{name:'C'}]

then after 3 seconds it should return array

 [{name:'D'},{name:'E'},{name:'F'}]

And so on also when the arrays gets end repeat the loop again.

I tried using chunk where i used slice and filter but that just return me an array of chunks together.

Thanks so much

A function cannot return multiple things at different times. What exactly are you looking for? Do you want to use a callback? — Bergi
– Bergi, Commented Jun 8, 2017 at 23:19

adrice727 · Accepted Answer · 2017-06-08 22:41:14Z

2

You can do this with a generator:

// Takes an array and the of the slice/subarray
function* subArray(array, size) {
  let i = 0;
  let remaining = true;
  while (remaining) {
    yield array.slice(i, i + size);
    i += size;
    if (i >= array.length) {
      remaining = false;
    }
  }
}

// Takes an array, a subarray size, and an interval in seconds
const getSubArraysAtInterval = (array, size, seconds) => {
  const iter = subArray(array, size);
  const interval = setInterval(() => {
    const next = iter.next();
    if (next.done) {
      clearInterval(interval);
      console.log('No values remaining');
    } else {
      console.log(next.value);
    }
  }, seconds * 1000)
}

getSubArraysAtInterval([1, 2, 3, 4, 5, 6], 3, 3);

Working fiddle: https://jsfiddle.net/adrice727/msx3sf03/1/

answered Jun 8, 2017 at 22:41

adrice727

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1 Comment

Muhammad Ahsan Over a year ago

Awesome, that looks really good. How about the looping? I just want to get it started again from first element when ends.

Dominic Tracey · Accepted Answer · 2017-06-09 01:04:06Z

1

const array = [{name:'A'},{name:'B'},{name:'C'},{name:'D'},{name:'E'},
{name:'F'},{name:'G'},{name:'H'},{name:'I'}];

let i = 0
setInterval(() => {
  console.log(array.slice(i,i+3))
  i*3 > array.length ? i=0 : i += 3
}, 3000)

The jsbin: https://jsbin.com/yoqelu/edit?html,js,console,output

edited Jun 9, 2017 at 1:04

answered Jun 8, 2017 at 22:34

Dominic Tracey

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2 Comments

RobG Over a year ago

It seems to me that i*3 is increasing geometrically but i += 3 is increasing linearly.

Dominic Tracey Over a year ago

That is the check for the end of the array, in which case the counter is reset. I added a jsbin to the answer.

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