Javascript Fundamentals

Alerts and Prompts

Using JS, we can display alerts and prompts on the screen. Here are the four ways to do so:

1. console: We can display messages in the browser console using the console.log() method.
2. dialog box: We can display alerts and prompts using dialog boxes using methods like alert(), confirm(), and prompt().
3. writing HTML element: We can write to an HTML element using its ID using the getElementById() method.
4. writing to the browser window: We can write directly to the browser window using the document.write() method.

Variables

In JavaScript, we declare variables using the var keyword. Here are some rules to follow when naming variables:

• Variable names can only contain letters, digits, underscores, and dollar signs.
• Variable names cannot start with a digit.
• Variable names are case-sensitive.
• It is a good practice to use descriptive and meaningful names for your variables.

Some data types in JavaScript include numbers (integers and floats), strings, and arrays.

Arrays

Arrays are a data structure in JavaScript that can hold multiple values in a single variable. Here are some basic operations we can perform with arrays:

1. We can create an array using the var keyword and assigning values to it inside square brackets.
2. We can access the values of an array using its index using square brackets.
3. We can add elements to an array using the push() method.
4. We can remove the last element of an array using the pop() method.
5. We can remove the first element of an array using the shift() method.
6. We can get the length of an array using the length property.
7. We can loop through an array using for and forEach loops.
8. We can join elements of an array into a string using the join() method.
9. We can split a string into an array using the split() method.
10. We can concatenate multiple arrays using the concat() method.
11. We can get the index of an element in an array using the indexOf() method.
12. We can get the last index of an element in an array using the lastIndexOf() method.

Functions

Functions are blocks of code that perform a specific task. We can define functions using the function keyword. Here are some concepts related to functions:

• We can call a function using its name followed by parentheses.
• We can pass arguments to a function inside the parentheses.
• A function can return a value using the return keyword.
• Variables declared inside a function are only accessible within the function (they have a local scope).
• Functions can be defined as function declarations or function expressions.
• Arrow functions are a newer syntax for defining functions that have a more concise syntax and lexically bind the this keyword.
• Functions can also be used as arguments to other functions, which is known as higher-order functions.

Objects

Objects are a complex data type in JavaScript that can hold multiple values and functions. Here are some basic concepts related to objects:

• Objects are defined using curly braces {} and can contain properties and methods.
• Properties are key-value pairs that represent the state of an object.
• Methods are functions that can be called on an object to perform specific tasks.
• We can access object properties using dot notation or bracket notation.
• We can add or modify object properties using dot notation or bracket notation.
• We can delete object properties using the delete keyword.
• We can check if an object has a property using the hasOwnProperty() method.
• We can get all the keys or values of an object using the Object.keys() or Object.values() method, respectively.
• We can create objects using constructor functions or classes.
• JavaScript also has some built-in objects like Math and Date.

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