Javascript - Array,String, Functions,Types of variables
ARRAY:
--> An array in JavaScript is a data structure used to store multiple values in a single variable.
--> Arrays can hold different types of data, including numbers, strings, objects, and even other arrays.
--> They are zero-indexed, meaning the first element is at index 0.
Creating an Array:
1. Using square brackets-[]
Ex:
1 |
|
2. Using the Array constructor-new Array
Ex:
1 2 |
|
Output:
[1, 2, 3, 4]
String
--> In JavaScript, a string is a sequence of characters used to represent text.
--> Strings in JavaScript are immutable, they cannot be changed.
Declaring Strings
Strings can be defined using:
1 2 3 |
|
Note:
--> Strings created with single or double quotes work the same.
--> There is no difference between the two.
--> Templates are strings enclosed in backticks(``)
--> Templates allow single and double quotes inside a string.
String Methods:
- trim() - Removes whitespace from both ends of a string.
- toLowerCase() - Converts all characters in a string to lowercase.
- toUpperCase() - Converts all characters in a string to uppercase.
- includes() - Checks if a substring exists within the string.
- indexOf() - Finds the index of the first occurrence of a substring.
- replace() - Replaces the first occurrence of a substring with another.
- replaceAll() - Replaces all occurrences of a substring with another.
- split() - Splits a string into an array based on a separator.
- substring() - Extracts a portion of the string between two indices.
- slice() - Extracts a part of a string using start and end indices.
- startsWith() - Checks if a string starts with a specific substring.
- endsWith() - Checks if a string ends with a specific substring.
- match() - Matches the string against a regular expression.
- padStart() - Pads the string from the start with a specific character.
- padEnd() - Pads the string from the end with a specific character.
- concat() - Combines two or more strings into one.
- toString() - Converts a value to a string.
- localeCompare() - Compares two strings for sorting based on locale.
- charAt() - Returns the character at a specific index in the string.
- charCodeAt() - Method returns the code of the character at a specified index in a string
- length - Retrieves the number of characters in the string.
Functions
--> A function is a block of reusable code that performs a specific task.
--> It executes the block of code only when it is called.
--> Function is defined with the function keyword, followed by a name, followed by parentheses ().
--> Function names can contain letters, digits, underscores, and dollar signs (same rules as variables).
--> The parentheses may include parameter names separated by commas:
(parameter1, parameter2, ...)
Syntax:
function name(parameter1, parameter2, parameter3) {
// code to be executed
}
Function Return
The return statement in JavaScript is used inside a function to return a value to the point where the function was called.
Types of variables:
- Global variable
- Local variable
Switch Statement:
--> The switch statement in JavaScript is used to execute different blocks of code based on different values of an expression.
--> It is an alternative to writing multiple if...else statements when dealing with multiple conditions.
--> switch statement is used to select one of many code blocks to be executed.
How it works?
- The switch expression is evaluated once.
- The value of the expression is compared with the values of each case.
- If there is a match, the associated block of code is executed.
- If there is no match, the default code block is executed.
Syntax:
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