Array

Welcome to the Array section of JDCodebase! Arrays are one of the most fundamental and frequently used data structures in programming...

What You’ll Learn

arr.push(val): Adds an element to the end of the array.

Before: [1, 2]
Code: arr.push(3);
After: [1, 2, 3]

arr.pop(): Removes the last element.

Before: [1, 2, 3]
Code: arr.pop();
After: [1, 2]

arr.shift(): Removes the first element of the array.

Before: [10, 20, 30]
Code: arr.shift();
After: [20, 30]

arr.unshift(val): Adds one or more elements to the beginning.

Before: [2, 3]
Code: arr.unshift(1);
After: [1, 2, 3]

arr.slice(start, end): Returns a shallow copy of a portion of the array.

Before: [10, 20, 30, 40]
Code: arr.slice(1, 3);
After: [20, 30]

arr.splice(index, count, ...items): Adds/removes items to/from the array at a specific index.

Before: [1, 2, 4]
Code: arr.splice(2, 0, 3);
After: [1, 2, 3, 4]

arr.includes(val): Checks if the array contains the specified value.

Before: [1, 2, 3]
Code: arr.includes(2);
After: true

arr.indexOf(val): Returns the first index of the specified value, or -1.

Before: [1, 2, 3, 2]
Code: arr.indexOf(2);
After: 1

arr.sort(): Sorts the array as strings by default.

Before: [3, 1, 2]
Code: arr.sort();
After: [1, 2, 3]

arr.reverse(): Reverses the elements of the array in place.

Before: [1, 2, 3]
Code: arr.reverse();
After: [3, 2, 1]

Let’s reverse an array using a loop.

function reverseArray(arr) {
  let result = [];
  for (let i = arr.length - 1; i >= 0; i--) {
    result.push(arr[i]);
  }
  return result;
}

Input: [1, 2, 3]

Expected Output: [3, 2, 1]