Shift last given number of elements to front of array JavaScript

Javascript Web Development Object Oriented Programming

Let’s say, we have to write an Array function, say prependN() that takes in a number n (n <= length of array the function is used with) and it takes n elements from the end and puts them in front of the array.

We have to do this in place and the function should only return a boolean based on the successful completion or failure of the task.

For example −

// if the input array is:
const arr = ["blue", "red", "green", "orange", "yellow", "magenta",
"cyan"];
// and the number n is 3,
// then the array should be reshuffled like:
const output = ["yellow", "magenta", "cyan", "blue", "red", "green",
"orange"];
// and the return value of function should be true

Now, let’s write the code for this function −

Example

const arr = ["blue", "red", "green", "orange", "yellow", "magenta",
"cyan"];
Array.prototype.reshuffle = function(num){
const { length: len } = this;
   if(num > len){
      return false;
   };
   const deleted = this.splice(len - num, num);
   this.unshift(...deleted);
   return true;
};
console.log(arr.reshuffle(4));
console.log(arr);

Output

The output in the console will be −

true
[
   'orange', 'yellow',
   'magenta', 'cyan',
   'blue', 'red',
   'green'
]

AmitDiwan

Published on 28-Aug-2020 13:35:39

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