JavaScript: Get removed elements of an given array until the passed function returns true

JavaScript fundamental (ES6 Syntax): Exercise-128 with Solution

Remove Elements Until Function True

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

• Loop through the array, 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 a function 'takeWhile' to retrieve elements from an array until a condition is no longer met
const takeWhile = (arr, func) => {
  // Iterate over the array using entries() to get both index and value
  for (const [i, val] of arr.entries())
    // If the condition function returns false for the current value, return the slice of the array up to this index
    if (func(val)) return arr.slice(0, i);
  // If the condition is true for all elements, return the original array
  return arr;
};
// Test the 'takeWhile' function by retrieving elements from an array while the condition is met
console.log(takeWhile([1, 2, 3, 4], n => n >= 3)); // Output: [1, 2]

Output:

[1,2]

Flowchart:

Live Demo:

See the Pen javascript-basic-exercise-128-1 by w3resource (@w3resource) on CodePen.

For more Practice: Solve these Related Problems:

• Write a JavaScript program that removes elements from the beginning of an array until a provided function returns true.
• Write a JavaScript function that iteratively shifts elements off an array until the condition is met and returns the removed elements.
• Write a JavaScript program that uses a while loop to drop elements from an array until the predicate evaluates to true for an element.

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