Javascript Basics

Common JavaScript Built-in Functions Explained JavaScript has many built-in functions that help with selecting, modifying content and performing calculations. Here are some examples of such built-in functions. DOM Manipulation Functions getElementById(id) – Selects a single HTML element by its id. This is one of the most common ways to interact with elements in the DOM. getElementsByClassName(className) – Selects all elements that have the specified class name(s). Returns an HTMLCollection. getElementsByTagName(tagName) – Returns all elements in the document that match a specific tag name (e.g., div, p). querySelector(selector) – Selects the first element that matches a given CSS selector. createElement(tagName) – Creates a new HTML element dynamically using JavaScript. Number Parsing Functions parseInt(string) – Converts a string into an integer (whole number). parseFloat(string) – Converts a string into a floating-point number (decimal). Function Binding and Array Methods bind() – Creates a new function that remembers a specific context, similar to putting a sticky note on a function to remind it of a specific this value. push(value) – Adds an item to the end of an array. pop() – Removes the last item from an array. sort() – Sorts an array in ascending or descending order. shift() – Removes the first item from an array. unshift(value) – Adds an item to the beginning of an array. Math Functions Math.abs(number) – Converts a number to its absolute (positive) value. Math() – A built-in JavaScript object that provides various mathematical functions and constants. Other Useful Functions getRootNode() – Retrieves the root (top-most) element in the DOM tree. console.error(message) – Displays an error message in the browser’s developer console. addEventListener(event, function) – Listens for a specific event (like a click) on a webpage and executes a function when the event occurs. eval(string) – Executes JavaScript code written inside a string (Use with caution due to security risks). escape(string) – Encodes a string for safe transfer over the internet. document.write(content) – Writes content directly onto a webpage (Not recommended for modern web development). length – Returns the number of elements in an array or the number of characters in a string

Mar 7, 2025 - 03:18

Common JavaScript Built-in Functions Explained

JavaScript has many built-in functions that help with selecting, modifying content and performing calculations. Here are some examples of such built-in functions.

DOM Manipulation Functions

getElementById(id) – Selects a single HTML element by its id. This is one of the most common ways to interact with elements in the DOM.
getElementsByClassName(className) – Selects all elements that have the specified class name(s). Returns an HTMLCollection.
getElementsByTagName(tagName) – Returns all elements in the document that match a specific tag name (e.g., div, p).
querySelector(selector) – Selects the first element that matches a given CSS selector.
createElement(tagName) – Creates a new HTML element dynamically using JavaScript.

Number Parsing Functions

parseInt(string) – Converts a string into an integer (whole number).
parseFloat(string) – Converts a string into a floating-point number (decimal).

Function Binding and Array Methods

bind() – Creates a new function that remembers a specific context, similar to putting a sticky note on a function to remind it of a specific this value.
push(value) – Adds an item to the end of an array.
pop() – Removes the last item from an array.
sort() – Sorts an array in ascending or descending order.
shift() – Removes the first item from an array.
unshift(value) – Adds an item to the beginning of an array.

Math Functions

Math.abs(number) – Converts a number to its absolute (positive) value.
Math() – A built-in JavaScript object that provides various mathematical functions and constants.

Other Useful Functions

getRootNode() – Retrieves the root (top-most) element in the DOM tree.
console.error(message) – Displays an error message in the browser’s developer console.
addEventListener(event, function) – Listens for a specific event (like a click) on a webpage and executes a function when the event occurs.
eval(string) – Executes JavaScript code written inside a string (Use with caution due to security risks).
escape(string) – Encodes a string for safe transfer over the internet.
document.write(content) – Writes content directly onto a webpage (Not recommended for modern web development).
length – Returns the number of elements in an array or the number of characters in a string