JavaScript: Get removed elements from the end of a given array until the passed function returns true

JavaScript fundamental (ES6 Syntax): Exercise-129 with Solution

Remove Elements from End Until True

Write a JavaScript program to get removed elements from the end of a given array until the passed function returns true.

• Create a reversed copy of the array, using the spread operator (...) and Array.prototype.reverse().
• Loop through the reversed copy, using a for...of loop over Array.prototype.entries() until the returned value from the function is falsy.
• Return the removed elements, using Array.prototype.slice().
• The callback function, fn, accepts a single argument which is the value of the element.

Sample Solution:

JavaScript Code:

//#Source https://bit.ly/2neWfJ2 

// Define the 'takeRightWhile' function.
const takeRightWhile = (arr, func) => {
  // Reverse the array and iterate through its keys.
  for (let i of arr.reverse().keys()) {
    // If the function returns false for the current value, return the slice of the original array from the end up to that index.
    if (!func(arr[i])) return arr.reverse().slice(arr.length - i, arr.length);
  }
  // If the function returns true for all elements, return the original array.
  return arr;
};

// Test the 'takeRightWhile' function.
console.log(takeRightWhile([1, 2, 3, 4], n => n < 3)); // Output: [3, 4]

Output:

[3,4]

Flowchart:

Live Demo:

See the Pen javascript-basic-exercise-129-1 by w3resource (@w3resource) on CodePen.

For more Practice: Solve these Related Problems:

• Write a JavaScript program that removes elements from the end of an array until a specified function returns true.
• Write a JavaScript function that pops elements off an array until a condition is met, returning the removed elements.
• Write a JavaScript program that iterates backward over an array and removes trailing elements until a predicate is satisfied.

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