9 Questions
What will be the result of the following code snippet: let x = 10; let y = '20'; let z = x + y;?
'1020' (a string)
Which method is used to find the length of a string in JavaScript?
length()
What will be the output of the code: let text = 'John Doe'; text.replace('John', 'Jane');?
'Jane Doe'
Which method can be used to remove elements from an array in JavaScript?
splice method
To add elements to an array in JavaScript, which method is commonly used?
splice method
Which method is suitable for copying elements from an existing array without changing the original array in JavaScript?
slice method
What will be the result of the following code snippet in JavaScript: const nums = [1, 2, 3, 4]; nums.splice(1, 2); nums;
[1, 3, 4]
When using the slice() method to copy an array in JavaScript, what will be the output of the following code snippet: const colors = ['red', 'blue', 'green']; const colorsCopy = colors.slice(); colorsCopy.push('yellow'); colors;
['red', 'blue', 'green']
When creating an array in JavaScript, which of the following is true?
Array literal syntax is preferred over Array constructor syntax for efficiency.
Study Notes
JavaScript Array
- An array is a special type of variable that stores multiple values using a special syntax.
- Every value is associated with a numeric index starting with 0.
Creating an Array
- An array can be created using two ways:
- Array literal syntax:
var stringArray = ["one", "two", "three"]; - Array constructor syntax:
var numericArray = new Array(3);
- Array literal syntax:
- Example of creating an array using array literal syntax:
const ITClass = ["whiteboard", "SlideShow", "Chairs"];
Accessing Array Elements
- An array element can be accessed using an index (key) with a zero-based index.
- Specify an index in square brackets
[]with an array name to access the element at a particular index.
Array Methods
- Adding an element to an array:
-
push(): adds an item to the end of an array -
unshift(): adds an item to the beginning of an array
-
- Removing an element from an array:
-
pop(): removes an item from the end of an array -
shift(): removes an item from the beginning of an array
-
-
deleteoperator: deletes an element from an array -
splice(): adds new items to an array and removes existing items -
slice(): creates a copy of an array -
concat(): merges (concatenates) existing arrays
Notes on Arrays
- An array can only have a numeric index (key).
- An array index must be numeric.
- A single array can store values of different data types.
Difference between Array and Object in JS
- Array: a collection of values, can store multiple values of different data types.
- Object: a collection of related data, consists of several variables.
Number
- Not mentioned in the provided text.
String
- Not mentioned in the provided text.
Test your knowledge on JavaScript arrays and accessing array elements with this quiz. Learn how arrays are useful for storing multiple values, condensing and organizing code, and containing different data types.
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