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JavaScript: Get the first element of an array

JavaScript Array: Exercise-3 with Solution

Write a JavaScript function to get the first element of an array. Passing a 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]]

Pictorial Presentation:

JavaScript: Get the first element of an array

Sample Solution:

HTML Code:

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Get the first element of an array</title>
</head>
<body>
</body>
</html>

JavaScript Code:

var first =  function(array, n) {
      if (array == null) 
      return void 0;
    if (n == null) 
      return array[0];
    if (n < 0)
      return [];
    return array.slice(0, n);
  };

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));

Sample Output:

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

Flowchart:

Flowchart: JavaScript : Get the first element of an array

ES6 Version:

var first =  (array, n) => {
      if (array == null) 
      return void 0;
    if (n == null) 
      return array[0];
    if (n < 0)
      return [];
    return array.slice(0, n);
  };

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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Previous: Write a JavaScript function to clone an array.
Next: Write a JavaScript function to get the last element of an array. Passing a parameter 'n' will return the last 'n' elements of the array.

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JavaScript: Tips of the Day

How to insert an item into an array at a specific index (JavaScript)?

What you want is the splice function on the native array object.

arr.splice(index, 0, item); will insert item into arr at the specified index (deleting 0 items first, that is, it's just an insert). In this example we will create an array and add an element to it into index 2:

var arr = [];
arr[0] = "Jani";
arr[1] = "Hege";
arr[2] = "Stale";
arr[3] = "Kai Jim";
arr[4] = "Borge";

console.log(arr.join());
arr.splice(2, 0, "Lene");
console.log(arr.join());

Ref: https://bit.ly/2BXbp04