pretty-print JSON using JavaScript

Question

How can I display JSON in an easy-to-read (for human readers) format? I\'m looking primarily for indentation and whitespace, with perhaps even colors / font-styles / etc.

Answer 1

I ran into an issue today with @Pumbaa80's code. I'm trying to apply JSON syntax highlighting to data that I'm rendering in a Mithril view, so I need to create DOM nodes for everything in the JSON.stringify output.

I split the really long regex into its component parts as well.

render_json = (data) ->
  # wraps JSON data in span elements so that syntax highlighting may be
  # applied. Should be placed in a `whitespace: pre` context
  if typeof(data) isnt 'string'
    data = JSON.stringify(data, undefined, 2)
  unicode =     /"(\\u[a-zA-Z0-9]{4}|\\[^u]|[^\\"])*"(\s*:)?/
  keyword =     /\b(true|false|null)\b/
  whitespace =  /\s+/
  punctuation = /[,.}{\[\]]/
  number =      /-?\d+(?:\.\d*)?(?:[eE][+\-]?\d+)?/

  syntax = '(' + [unicode, keyword, whitespace,
            punctuation, number].map((r) -> r.source).join('|') + ')'
  parser = new RegExp(syntax, 'g')

  nodes = data.match(parser) ? []
  select_class = (node) ->
    if punctuation.test(node)
      return 'punctuation'
    if /^\s+$/.test(node)
      return 'whitespace'
    if /^\"/.test(node)
      if /:$/.test(node)
        return 'key'
      return 'string'

    if /true|false/.test(node)
      return 'boolean'

     if /null/.test(node)
       return 'null'
     return 'number'
  return nodes.map (node) ->
    cls = select_class(node)
    return Mithril('span', {class: cls}, node)

Code in context on Github here

Answer 2

Couldn't find any solution that had good syntax highlighting for the console, so here's my 2p

Install & Add cli-highlight dependency

npm install cli-highlight --save

Define logjson globally

const highlight = require('cli-highlight').highlight
console.logjson = (obj) => console.log(
                               highlight( JSON.stringify(obj, null, 4), 
                                          { language: 'json', ignoreIllegals: true } ));

Use

console.logjson({foo: "bar", someArray: ["string1", "string2"]});

Answer 3

I use the JSONView Chrome extension (it is as pretty as it gets :):

Edit: added jsonreport.js

I've also released an online stand-alone JSON pretty print viewer, jsonreport.js, that provides a human readable HTML5 report you can use to view any JSON data.

You can read more about the format in New JavaScript HTML5 Report Format.

Answer 4

To highlight and beautify it in HTML using Bootstrap:

function prettifyJson(json, prettify) {
    if (typeof json !== 'string') {
        if (prettify) {
            json = JSON.stringify(json, undefined, 4);
        } else {
            json = JSON.stringify(json);
        }
    }
    return json.replace(/("(\\u[a-zA-Z0-9]{4}|\\[^u]|[^\\"])*"(\s*:)?|\b(true|false|null)\b|-?\d+(?:\.\d*)?(?:[eE][+\-]?\d+)?)/g,
        function(match) {
            let cls = "<span>";
            if (/^"/.test(match)) {
                if (/:$/.test(match)) {
                    cls = "<span class='text-danger'>";
                } else {
                    cls = "<span>";
                }
            } else if (/true|false/.test(match)) {
                cls = "<span class='text-primary'>";
            } else if (/null/.test(match)) {
                cls = "<span class='text-info'>";
            }
            return cls + match + "</span>";
        }
    );
}

Answer 5

You can use JSON.stringify(your object, null, 2) The second parameter can be used as a replacer function which takes key and Val as parameters.This can be used in case you want to modify something within your JSON object.

more reference : https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/stringify

Answer 6

This is nice:

https://github.com/mafintosh/json-markup from mafintosh

const jsonMarkup = require('json-markup')
const html = jsonMarkup({hello:'world'})
document.querySelector('#myElem').innerHTML = html

HTML

<link ref="stylesheet" href="style.css">
<div id="myElem></div>

Example stylesheet can be found here

https://raw.githubusercontent.com/mafintosh/json-markup/master/style.css