Javascript Array formatting

Question

I am new to javascript, recently I am studying javascript array and object.

if I have a object

const initialValue = {
  a: 30,
  b: 40,
  c: 50
}

const initialValueKey = Object.keys(initialValue)

const [, , , ...value] = initialValueKey;

I wonder what is this [, , , ...value] expression, I know ...is spread operator, but i'm not sure what the value of [, , , ...value] here.

It's skipping the first 3 values and assigning the rest of the array to value. Try making your initialValue with more properties to see the difference — Phil
– Phil, Commented Jul 15, 2020 at 3:48
it's a complicated way to write const value = initialValueKey.slice(3); — Thomas
– Thomas, Commented Jul 15, 2020 at 3:48

yqlim · Accepted Answer · 2020-07-15 03:48:16Z

3

It is a way to retrieve "other values", or retrieving the values and skipping the first n.

Here's an example:

const obj = {
  a: 1,
  b: 2,
  c: 3,
  d: 4,
  e: 5
};

const data = Object.keys(obj);

const [,,, ...values] = data;

console.log(values);

answered Jul 15, 2020 at 3:48

yqlim

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Sachintha Nayanajith · Accepted Answer · 2020-07-15 04:57:40Z

0

This is a way to assign the variables to arrays. the two commas in this example skipsthe first 2 elements

const initialValue = {
  a: 30,
  b: 40,
  c: 50,
  d: 70
}

const initialValueKey = Object.keys(initialValue)

const [, , ...value] = initialValueKey;

console.log(value);

answered Jul 15, 2020 at 4:57

Sachintha Nayanajith

7315 silver badges12 bronze badges

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