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How to Create an Empty Array of a Given Size with JavaScript?

Sometimes, we want to create an empty array of a given size with JavaScript.

In this article, we’ll look at how to create an empty array of a given size with JavaScript.

Create an Empty Array of a Given Size with JavaScript

To create an empty array of a given size with JavaScript, we can use the Array constructor.

For instance, we can write:

const arr = new Array(5);  
console.log(arr.length)

to create an empty array with length 5 by passing in the length as the argument for the Array constructor.

Therefore, arr.length is 5 according to the console log.

Conclusion

To create an empty array of a given size with JavaScript, we can use the Array constructor.

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JavaScript Answers

How to Assign Multiple Variables to the Same Value with JavaScript?

Sometimes, we want to assign multiple variables to the same value with JavaScript.

In this article, we’ll look at how to assign multiple variables to the same value with JavaScript.

Assign Multiple Variables to the Same Value with JavaScript

To assign multiple variables to the same value with JavaScript, we can use the destructuring syntax.

For instance, we can write:

const [
  moveUp,
  moveDown,
  moveLeft,
  moveRight,
  mouseDown,
  touchDown
] = Array(6).fill(false);

console.log(
  moveUp,
  moveDown,
  moveLeft,
  moveRight,
  mouseDown,
  touchDown
);

to destructure the values of the array that we created with Array(6).fill(false) .

Then we assign each value in the array to each variable on the left side.

Therefore, from the console log, we can see:

false false false false false false

logged.

Conclusion

To assign multiple variables to the same value with JavaScript, we can use the destructuring syntax.

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JavaScript Answers

How to Create an Array of All Integers Between Two Numbers, Inclusive, in JavaScript?

Sometimes, we want to create an array of all integers between two numbers, inclusive, in JavaScript.

In this article, we’ll look at how to create an array of all integers between two numbers, inclusive, in JavaScript.

Create an Array of All Integers Between Two Numbers, Inclusive, in JavaScript

To create an array of all integers between two numbers, inclusive, in JavaScript, we can use the Array.from method to create an array with a given length and includes integers between 2 numbers.

For instance, we can write:

const arr = Array.from({  
  length: 5  
}, (v, k) => k + 1)  
console.log(arr)

to call Array.from with an object with the length property to specify the length of the array.

The callback passed in as the 2nd argument returns a number that we want to include.

Therefore, arr is [1, 2, 3, 4, 5] .

Conclusion

To create an array of all integers between two numbers, inclusive, in JavaScript, we can use the Array.from method to create an array with a given length and includes integers between 2 numbers.

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How to Loop Through a Date Range with JavaScript?

Sometimes, we want to loop through a date range with JavaScript.

In this article, we’ll look at how to loop through a date range with JavaScript.

Loop Through a Date Range with JavaScript

To loop through a date range with JavaScript, we can use a while loop.

For instance, we can write:

const start = new Date("02/05/2020");  
const end = new Date("02/10/2020");  
let loop = new Date(start);  
while (loop <= end) {  
  console.log(loop);  
  const newDate = loop.setDate(loop.getDate() + 1);  
  loop = new Date(newDate);  
}

We create the start and end date objects that are the start and end dates of the date range.

loop is the variable with the start date.

We increment loop in the while loop until it’s bigger than or equal to end .

To do that, we write:

const newDate = loop.setDate(loop.getDate() + 1);  
loop = new Date(newDate);

Therefore, we see the dates in the date range being looped through and logged to the console.

Conclusion

To loop through a date range with JavaScript, we can use a while loop.

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JavaScript Answers

How to Extract Elements with an Even Index from an Array?

Sometimes, we want to extract elements with an even index from an array.

In this article, we’ll look at how to extract elements with an even index from an array.

Extract Even Elements of an Array

To extract elements with an even index from an array., we can use the array filter instance method.

For instance, we can write:

const arr = [4, 5, 7, 8, 14, 45, 76];
const filtered = arr.filter((element, index) => {
  return (index % 2 === 0);
});
console.log(arr)

to call filter with a callback that has index as the 2nd parameter.

We return index % 2 === 0 to filter out all the elements that have odd indexes.

Therefore, filtered is [4, 5, 7, 8, 14, 45, 76] .

Conclusion

To extract elements with an even index from an array., we can use the array filter instance method.