JavaScript: Get the first element of an array

JavaScript Array: Exercise-3 with Solution

First Elements of Array

Write a JavaScript function to get the first element of an array. Passing the parameter 'n' will return the first 'n' elements of the array.

Test Data:
console.log(array_Clone([1, 2, 4, 0]));
console.log(array_Clone([1, 2, [4, 0]]));
[1, 2, 4, 0]
[1, 2, [4, 0]]

Visual Presentation:

Sample Solution:

JavaScript Code:

// Function to get the first n elements of an array
var first = function(array, n) {
  // Check if the input array is null, return undefined if true
  if (array == null)
    return void 0;

  // Check if the value of n is null, return the first element of the array if true
  if (n == null)
    return array[0];

  // Check if the value of n is negative, return an empty array if true
  if (n < 0)
    return [];

  // Use the slice method to get the first n elements of the array
  return array.slice(0, n);
};

// Testing the function with various cases
console.log(first([7, 9, 0, -2]));
console.log(first([], 3));
console.log(first([7, 9, 0, -2], 3));
console.log(first([7, 9, 0, -2], 6));
console.log(first([7, 9, 0, -2], -3));

Output:

7
[]
[7,9,0]
[7,9,0,-2]
[]

Flowchart:

ES6 Version:

// Function to get the first n elements of an array
const first = (array, n) => {
  // Check if the input array is null, return undefined if true
  if (array == null)
    return undefined;

  // Check if the value of n is null, return the first element of the array if true
  if (n == null)
    return array[0];

  // Check if the value of n is negative, return an empty array if true
  if (n < 0)
    return [];

  // Use the slice method to get the first n elements of the array
  return array.slice(0, n);
};

// Testing the function with various cases
console.log(first([7, 9, 0, -2]));
console.log(first([], 3));
console.log(first([7, 9, 0, -2], 3));
console.log(first([7, 9, 0, -2], 6));
console.log(first([7, 9, 0, -2], -3));

Live Demo:

See the Pen JavaScript - Get the first element of an array- array-ex-3 by w3resource (@w3resource) on CodePen.

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