JavaScript: Get the first element of an array

Last update on May 30 2022 10:07:19 (UTC/GMT +8 hours)

JavaScript Array: Exercise-1 with Solution

Write a JavaScript function to check whether an 'input' is an array or not.

Test Data:
console.log(is_array('w3resource'));
console.log(is_array([1, 2, 4, 0]));
false
true

Sample Solution:

HTML Code:

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>JS Bin</title>
</head>
<body>
</body>
</html>

JavaScript Code:

var is_array = function(input) {
  if (toString.call(input) === "[object Array]")
    return true;
  return false;   
    };
console.log(is_array('w3resource'));
console.log(is_array([1, 2, 4, 0]));

Sample Output:

false
true

Flowchart:

ES6 Version:

var is_array = input => {
  if (toString.call(input) === "[object Array]")
    return true;
  return false;   
    };
console.log(is_array('w3resource'));
console.log(is_array([1, 2, 4, 0]));

Live Demo:

See the Pen JavaScript - Get the first element of an array- array-ex-1 by w3resource (@w3resource) on CodePen.

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Next: Write a JavaScript function to clone an 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