JS Formatter

Free Online JS Formatter -- Six JavaScript Tools in One

This page provides six browser-based JavaScript utilities accessible from the left sidebar. Every tool runs entirely in your browser -- nothing is uploaded, nothing is stored, and no account is required. Choose a tool from the sidebar, paste your code or text, and the output appears automatically.

Online JS Formatter -- Beautify JavaScript with Indent Control

Minified or machine-generated JavaScript is nearly impossible to read. The JS Formatter takes compact or unformatted JavaScript and restructures it with your chosen indent size -- 2 spaces, 4 spaces, or a real tab character. The output updates automatically as you type, so you see the formatted result immediately.

How the JS Formatter Works

The formatter uses the js-beautify library, loaded from a public CDN, to parse and reformat your JavaScript. js-beautify understands modern JavaScript syntax including arrow functions, destructuring assignments, template literals, async/await, class declarations, and ES module syntax. It preserves the logical structure of your code while adding consistent whitespace and newlines to make it readable.

When to Format JavaScript

API responses sometimes include JavaScript snippets, build tools can output inlined or bundled scripts, and copy-pasted code from documentation often arrives with inconsistent spacing. Formatting before debugging or reviewing code makes it significantly easier to follow control flow, spot missing brackets, and understand nested structures.

JS Minifier -- Compact JavaScript for Production

The JS Minifier removes single-line comments, block comments, and unnecessary whitespace from JavaScript code, producing a compact version that is smaller and faster to parse. The code structure, variable names, and logic remain identical to the original.

What the Minifier Removes

The minifier strips all text following // on a line (single-line comments), all text between /* and */ (block comments), leading and trailing whitespace on every line, and consecutive blank lines. The result is code that occupies far fewer bytes without altering its runtime behavior.

Why Minify JavaScript

Smaller JavaScript files download faster over the network, reduce the amount of data the browser must parse before executing, and consume less bandwidth -- a factor in both mobile performance and server costs. Minification is a standard step in every front-end build pipeline. For projects without a build tool, this online minifier provides a quick alternative.

JS Validator -- Check JavaScript Syntax Instantly

The JS Validator checks whether your JavaScript is syntactically correct by attempting to compile it using the browser's built-in JavaScript engine. If the code is valid, the validator reports the total line count and character count. If the code contains a syntax error, the exact error message from the engine is shown so you can find and fix the problem.

What the Validator Checks

The validator detects syntax errors only -- it does not execute the code, so runtime errors such as undefined variables, type mismatches, or logic errors will not be reported. What it catches reliably is missing closing braces or brackets, unclosed string literals, unexpected tokens, use of reserved keywords as identifiers, and other structural problems that prevent the JavaScript engine from parsing the file.

Common JavaScript Syntax Errors

The most frequent syntax errors in JavaScript are missing closing curly braces after a function or if block, a missing comma between object properties or function arguments, a string that opens with a quote character and never closes, and a typo in a control-flow keyword such as writing funciton instead of function. The validator catches all of these and shows the engine's own error text, which typically includes the line number where parsing failed.

JS Escape -- Embed Text Safely in JavaScript Strings

The JS Escape tool takes plain text and produces a properly escaped JavaScript string literal, including surrounding single quotes. Any character that would break a JavaScript string -- single quotes, double quotes, backslashes, newlines, carriage returns, tabs, and Unicode control characters -- is replaced with the correct JavaScript escape sequence.

When You Need JS String Escaping

Common situations where escaping is necessary include embedding multi-line error messages in a JavaScript variable, embedding Windows file paths that contain backslashes, including user-generated text in a script tag, and embedding code snippets that contain quote characters. The output from this tool can be pasted directly into any JavaScript file as the value of a string variable.

Escape Sequences Produced

Single quotes become \', double quotes become \", backslashes become \\, newlines become \n, carriage returns become \r, tabs become \t, and control characters below U+001F become Unicode escape sequences in the form \u00XX. The output is a complete single-quoted string literal ready to use in JavaScript.

JS to JSON Converter -- Convert JavaScript Object Literals to Strict JSON

JavaScript object and array literals are often written with conveniences that are not valid in strict JSON: unquoted property keys, single-quoted strings, trailing commas after the last item, and inline comments. The JS to JSON converter takes these informal JavaScript structures and converts them to valid, strict JSON that any JSON parser can consume.

Differences Between JS Object Literals and JSON

JSON is a strict data interchange format derived from JavaScript syntax. It requires all property keys and string values to use double quotes, prohibits trailing commas after the last element in arrays and objects, does not allow JavaScript-style comments, and does not permit undefined as a value. A JavaScript object literal, by contrast, allows unquoted keys, single or double quotes, trailing commas, comments, and a wider range of values. The converter handles the common cases automatically.

Practical Use Cases

Configuration files such as package.json alternatives, fixture files written in JavaScript module format, and data copied from browser console output are frequent candidates for this conversion. If the input contains function expressions, class instances, or other constructs that cannot be represented as pure data, the tool will show an error explaining why the conversion failed.

JS Analyzer -- Understand Your Code at a Glance

The JS Analyzer scans your JavaScript code and produces a structured report with counts for lines, characters, functions, arrow functions, variables, classes, control flow statements, and module imports and exports. This gives you a quick snapshot of a file's complexity without needing to run the code or set up a linter.

What the Report Includes

The report breaks down line counts into total lines, non-empty lines, comment lines (starting with // or *), and estimated code lines. The declarations section counts function keyword usages, arrow function patterns, and every var, let, and const declaration. Control flow counting covers if statements, for loops, while loops, and try blocks. The modules section counts import and export keywords.

Using the Analyzer for Code Review

Running the analyzer on a file before a review session gives a quick complexity estimate. Files with very high function counts relative to their line count may be doing too much in one place. Files with many control flow statements relative to their size may benefit from extraction or simplification. Comparing analyzer reports across files in a project can help identify outliers that need attention.

Related JavaScript and Code Tools

If you work with JavaScript and web code regularly, these tools on the site work well alongside this page:

• JSON Formatter -- format, minify, validate, and convert JSON in one place
• Code Formatter -- format HTML, CSS, JSON, XML, and JavaScript in one tool
• HTML Editor -- full CodeMirror editor with live preview and HTML validator
• AI Python Code Generator -- generate Python code with AI