In this article let us discuss about How To Use Browser Console In JavaScript.
Using Browser Console in JavaScript
Web developers and JavaScript learners need the browser console, commonly known as developer tools. It lets you view script-logged messages, run JavaScript commands, debug code, and interact with web page code.
Opening the Console
The browser console is usually accessed via the developer tools from the menu or a keyboard shortcut. Your operating system and browser may differ, but these are some typical steps:
- Pressing the F12 keypress.
- Right-click anywhere on the page and select “Inspect” or “Inspect element”.
- Using keyboard shortcuts:
- Chrome, Edge, and Windows/Linux: Ctrl+Shift+J.
- Windows/Linux, Chrome, Firefox, and Opera: Control + Shift + I; go to Console tab or hit ESC.
- (Mac, Chrome) Alt + Command + J.
- On Mac or Chrome, press Command + Option + J.
- Ctrl + Shift + K (Firefox, Windows/Linux).
- For Mac and Firefox, press Command + Option + K.
When the developer tools are opened, they frequently show up as a panel at the side, top, or bottom of the browser window, though occasionally they are displayed in a different window. There are several tabs in this panel, including “Console” and “Elements” (for HTML and CSS). To work with JavaScript, you must select the “Console” option.
Executing JavaScript Code Directly
You can input and run JavaScript code snippets directly from the console tab’s command line interface. To execute code, type it into the prompt (often denoted by a > symbol) and hit Enter. Shift + Enter can usually be used to advance to the next line when entering many lines of code prior to execution. The output or outcome of the code you run will be displayed in the console.
Logging Messages with
Simple and popular console commands include console.log(). It helps you debug and understand your code by printing variables, values, and messages to the console.
Console.log() supports many data types:
- Strings: “Hello world!” console.log(). “Hello world!” will appear on the console as a result.
- Variables: Any type of variable can be logged. To display the variable, just pass it.
- Multiple values: Several comma-separated values can be logged; these will be written on a single line with spaces between them. log([‘string’], 1, obj, window); in console.
- Objects: To examine an object’s characteristics, including the outcome of API calls, logging is helpful. console.log({ ‘Email’: ”,… });. In some debuggers, you can inspect properties and explore nested objects by clicking on the printed text or a little triangle to expand object details. A comprehensive interactive list of an object’s properties can be obtained with console.dir(object).
- HTML components: Console.log(document.body); is one way to log elements that are part of the DOM.
- String substitution: For strings, console.log() allows formatting with placeholders like %s. “%s %s”, “Hello”, “World!” console.log();.
console.log() usually returns undefined since it lacks an explicit return value.
Other Useful Console Methods
The console object offers a number of additional debugging and inspection techniques in addition to console.log():
Console.error(message…): Logs output and styles it to highlight errors. It frequently offers a stack trace.
- (message…) console.warn: creates a warning log.
- (message…) console.info: records a message with information.
- Logging a debugging message is done with console.debug(message…).
- You can examine nested objects and arrays by using console.dir(object), which shows an interactive list of an object’s attributes or components. DOM elements can also be output by it.
- console.dirxml(node): Shows a document node’s XML or HTML markup.
- A timer is started and stopped using console.time(label) and console.timeEnd(label), which log the amount of time that has passed to the console. helpful for calculating how long code takes to execute.
- console.trace(message): Displays the call route that resulted in the console.trace() call by printing a stack trace to the console.
- console.table(data): Shows tabular data on the console, such as arrays or objects.
- console.count(label): Records how many times the given label has been used to invoke this method.
- If the supplied expression is false or falsy, console.assert(expression, message): Shows an error message on the console.
- The console window is cleared using console.clear().
- console.group and console.group(message)Collapsed(message): Opens the console with a fresh set of collapsable messages. console.groupThe group is collapsed when Collapsed() is called. Until console.groupEnd() is called, all ensuing console output is represented as belonging to this group.
- console.groupEnd(): Closes the most recent console group that was launched.
Additionally, command line tools like $() (a abbreviation for document) are frequently available in browser consoles.For speedy element selection, $$() (a shortcut for document.querySelectorAll()) and getElementById() can be useful.
Debugging and Inspecting
Developers mainly utilise the console for debugging. The process of identifying and resolving issues when a program isn’t operating as intended is known as debugging. Understanding what is occurring in the code can be gained by logging logical messages to the console.
In addition to running code and seeing logged messages, the developer tools panel, which includes the console, lets you:
- View the error messages. The developer console displays an error message in the event that an unhandled exception occurs.
- Document Object Model (DOM) is a logical tree representation of HTML content. Use console.dir(document) or console.dir(element) to inspect DOM objects and their structure, usually under the Elements tab.
- Explore the Browser Object Model’s window, history, navigator, and location. Console.dir(window) inspects the window object. The window object contains the document object. Console.dir(history), console.dir(navigator), and console.dir(location) let you directly view history, navigator, and location.
- Use developer tools tab to set code breakpoints. Breakpoints enable you explore variables and go through your script by pausing execution at a line.
Compatibility Notes
The console object was only defined while the Developer Tools were open in Internet Explorer versions IE8 and below. This meant that if the tools weren’t open, console.log() statements might result in problems. To counteract this, programmers would frequently verify that the console object was present before utilising its functions, as in the following example: if (console) { console.log(“test”); }. This restriction is not present in contemporary browsers.
In conclusion, JavaScript code execution, testing, debugging, and comprehension inside the context of a web page depend on the browser console, a potent integrated development environment feature.
You can also refer How To Add JavaScript To A Web Page