Guess the indentation of a JSON string.

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Example

import guessJsonIndent from 'guess-json-indent'

const input = [{ example: true }]
guessJsonIndent(JSON.stringify(input)) // undefined
guessJsonIndent(JSON.stringify(input, undefined, 1)) // 1
guessJsonIndent(JSON.stringify(input, undefined, 2)) // 2
guessJsonIndent(JSON.stringify(input, undefined, 4)) // 4
guessJsonIndent(JSON.stringify(input, undefined, '\t')) // '\t'
guessJsonIndent(JSON.stringify(input, undefined, '\t\t')) // '\t\t'

// Keep the indentation of a JSON string when parsing/serializing it
const jsonString = JSON.stringify(input, undefined, 2)
const indent = guessJsonIndent(jsonString)
const parsedValue = JSON.parse(jsonString)
console.log(JSON.stringify(input, undefined, indent)) // Same as jsonString

Install

npm install guess-json-indent

This package works in both Node.js >=18.18.0 and browsers.

This is an ES module. It must be loaded using an import or import() statement, not require(). If TypeScript is used, it must be configured to output ES modules, not CommonJS.

API

guessJsonIndent(jsonString)

The return value is the same as the third argument to JSON.stringify():

• undefined: none
• integer: number of spaces
• string: tabs

Benchmarks

This library is very fast thanks to:

• Looking only at the first indented line, which is sufficient in the vast majority of real-life cases
• Being specific to JSON

The following benchmarks compares it:

• With detect-indent, detect-json-indent and detect-indentation
• On a big JSON string (8MB)

guess-json-indent:         43ns
detect-json-indent:  60114470ns
detect-indentation: 141975495ns
detect-indent:      198161087ns

Related projects

• truncate-json: Truncate a JSON string
• is-json-value: Check if a value is valid JSON
• safe-json-value: ⛑️ JSON serialization should never fail

Support

For any question, don't hesitate to submit an issue on GitHub.

Everyone is welcome regardless of personal background. We enforce a Code of conduct in order to promote a positive and inclusive environment.

Contributing

This project was made with ❤️. The simplest way to give back is by starring and sharing it online.

If the documentation is unclear or has a typo, please click on the page's Edit button (pencil icon) and suggest a correction.

If you would like to help us fix a bug or add a new feature, please check our guidelines. Pull requests are welcome!