JavaScript: Move the specified amount of elements to the end of the array

JavaScript fundamental (ES6 Syntax): Exercise-94 with Solution

Write a JavaScript program to move the specified amount of elements to the end of the array.

• Use Array.prototype.slice() twice to get the elements after the specified index and the elements before that.
• Use the spread operator (...) to combine the two into one array.
• If offset is negative, the elements will be moved from end to start.

Sample Solution:

JavaScript Code:

//#Source https://bit.ly/2neWfJ2
const offset = (arr, offset) => [...arr.slice(offset), ...arr.slice(0, offset)];
console.log(offset([1, 2, 3, 4, 5], 2));
console.log(offset([1, 2, 3, 4, 5], -2));

Sample Output:

[3,4,5,1,2]
[4,5,1,2,3]

Pictorial Presentation:

Flowchart:

Live Demo:

See the Pen javascript-basic-exercise-94-1 by w3resource (@w3resource) on CodePen.

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JavaScript: Tips of the Day

How to remove a specific item from an array?

Find the index of the array element you want to remove using indexOf, and then remove that index with splice.

The splice() method changes the contents of an array by removing existing elements and/or adding new elements.

const array = [2, 5, 9];

console.log(array);

const index = array.indexOf(5);
if (index > -1) {
array.splice(index, 1);
}

// array = [2, 9]
console.log(array);

The second parameter of splice is the number of elements to remove. Note that splice modifies the array in place and returns a new array containing the elements that have been removed.

For the reason of completeness, here are functions. The first function removes only a single occurrence (i.e. removing the first match of 5 from [2,5,9,1,5,8,5]), while the second function removes all occurrences:

function removeItemOnce(arr, value) {
var index = arr.indexOf(value);
if (index > -1) {
arr.splice(index, 1);
}
return arr;
}

function removeItemAll(arr, value) {
var i = 0;
while (i < arr.length) {
if (arr[i] === value) {
arr.splice(i, 1);
} else {
++i;
}
}
return arr;
}
//Usage
console.log(removeItemOnce([2,5,9,1,5,8,5], 5))
console.log(removeItemAll([2,5,9,1,5,8,5], 5))

Ref: https://bit.ly/2N9nKRp