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

Thanks a lot @all! Based on the previous answers, here is another variant method providing custom replacement rules as parameter:

 renderJSON : function(json, rr, code, pre){
   if (typeof json !== 'string') {
      json = JSON.stringify(json, undefined, '\t');
   }
  var rules = {
   def : 'color:black;',    
   defKey : function(match){
             return '' + match + '';
          },
   types : [
       {
          name : 'True',
          regex : /true/,
          type : 'boolean',
          style : 'color:lightgreen;'
       },

       {
          name : 'False',
          regex : /false/,
          type : 'boolean',
          style : 'color:lightred;'
       },

       {
          name : 'Unicode',
          regex : /"(\\u[a-zA-Z0-9]{4}|\\[^u]|[^\\"])*"(\s*:)?/,
          type : 'string',
          style : 'color:green;'
       },

       {
          name : 'Null',
          regex : /null/,
          type : 'nil',
          style : 'color:magenta;'
       },

       {
          name : 'Number',
          regex : /-?\d+(?:\.\d*)?(?:[eE][+\-]?\d+)?/,
          type : 'number',
          style : 'color:darkorange;'
       },

       {
          name : 'Whitespace',
          regex : /\s+/,
          type : 'whitespace',
          style : function(match){
             return ' ';
          }
       } 

    ],

    keys : [
       {
           name : 'Testkey',
           regex : /("testkey")/,
           type : 'key',
           style : function(match){
             return '
' + match + '
';
          }
       }
    ],

    punctuation : {
          name : 'Punctuation',
          regex : /([\,\.\}\{\[\]])/,
          type : 'punctuation',
          style : function(match){
             return '
________
';
          }
       }

  };

  if('undefined' !== typeof jQuery){
     rules = $.extend(rules, ('object' === typeof rr) ? rr : {});  
  }else{
     for(var k in rr ){
        rules[k] = rr[k];
     }
  }
    var str = json.replace(/([\,\.\}\{\[\]]|"(\\u[a-zA-Z0-9]{4}|\\[^u]|[^\\"])*"(\s*:)?|\b(true|false|null)\b|-?\d+(?:\.\d*)?(?:[eE][+\-]?\d+)?)/g, function (match) {
    var i = 0, p;
    if (rules.punctuation.regex.test(match)) {
               if('string' === typeof rules.punctuation.style){
                   return '' + match + '';
               }else if('function' === typeof rules.punctuation.style){
                   return rules.punctuation.style(match);
               } else{
                  return match;
               }            
    }

    if (/^"/.test(match)) {
        if (/:$/.test(match)) {
            for(i=0;i' + match + '';
               }else if('function' === typeof p.style){
                   return p.style(match);
               } else{
                  return match;
               }                
             }              
           }   
            return ('function'===typeof rules.defKey) ? rules.defKey(match) : '' + match + '';            
        } else {
            return ('function'===typeof rules.def) ? rules.def(match) : '' + match + '';
        }
    } else {
        for(i=0;i' + match + '';
               }else if('function' === typeof p.style){
                   return p.style(match);
               } else{
                  return match;
               }                
          }             
        }

     }

    });

  if(true === pre)str = '
' + str + '
';
  if(true === code)str = '' + str + '';
  return str;
 }