一 使用原生JSON.stringify實現

<textarea name="" id="myTA" cols="30" rows="10"></textarea>
<script>
    var myTA = document.getElementById("myTA");
    myTA.value = JSON.stringify({"aaa":123,"bbb":456}, null, 4)
</script>

二 自己寫函數實現

https://jsfiddle.net/q2gnX/

在線預覽

// Notes:
// - json2.js is not needed if browser supports JSON.stringify and JSON.parse natively
 

// - jQuery is only used to place the results
// colon；冒號，pad；填補
var formatJson = function(json, options) {
      var reg = null,
        formatted = ‘‘,
        pad = 0,
        PADDING = ‘    ‘; // one can also use ‘\t‘ or a different number of spaces

      // optional settings
      options = options ||
 
 {};
      // remove newline where ‘{‘ or ‘[‘ follows ‘:‘
      options.newlineAfterColonIfBeforeBraceOrBracket = (options.newlineAfterColonIfBeforeBraceOrBracket === true) ? true : false;
      // use a space after a colon
      options.spaceAfterColon = (options.spaceAfterColon === false) ? false : true
 
;
      
      // begin formatting...

      // make sure we start with the JSON as a string
      if (typeof json !== ‘string‘) {
        json = JSON.stringify(json);
      }
      // parse and stringify in order to remove extra whitespace
      // json = JSON.stringify(JSON.parse(json));可以除去多余的空格
      json = JSON.parse(json);
      json = JSON.stringify(json);

      // add newline before and after curly braces
      reg = /([\{\}])/g;
      json = json.replace(reg, ‘\r\n$1\r\n‘);

      // add newline before and after square brackets
      reg = /([\[\]])/g;
      json = json.replace(reg, ‘\r\n$1\r\n‘);
      
      // add newline after comma
      reg = /(\,)/g;
      json = json.replace(reg, ‘$1\r\n‘);
      
      // remove multiple newlines
      reg = /(\r\n\r\n)/g;
      json = json.replace(reg, ‘\r\n‘);
      
      // remove newlines before commas
      reg = /\r\n\,/g;
      json = json.replace(reg, ‘,‘);

      // optional formatting...
      if (!options.newlineAfterColonIfBeforeBraceOrBracket) {     
        reg = /\:\r\n\{/g;
        json = json.replace(reg, ‘:{‘);
        reg = /\:\r\n\[/g;
        json = json.replace(reg, ‘:[‘);
      }
      if (options.spaceAfterColon) {      
        reg = /\:/g;
        json = json.replace(reg, ‘: ‘);
      }

      $.each(json.split(‘\r\n‘), function(index, node) {
        var i = 0,
          indent = 0,
          padding = ‘‘;
        
        if (node.match(/\{$/) || node.match(/\[$/)) {
          indent = 1;
        } else if (node.match(/\}/) || node.match(/\]/)) {
          if (pad !== 0) {
            pad -= 1;
          }
        } else {
          indent = 0;
        }
      
        for (i = 0; i < pad; i++) {
          padding += PADDING;
        }
      
        formatted += padding + node + ‘\r\n‘;
        pad += indent;
      });
      
      return formatted;
};

var json = {};

// display formatted JSON (as JSON object)
json = {"a":{"aa":[1,2,{"aaa":"abc","bbb":"defgh","ccc":987},[100,200,300,{"one":1,"two":"ii","three":"Three"},1000]],"bb":"xyz","ccc":777},"b":["qqq","www","eee"],"c":"hello","d":12345};
$(‘#formattedJson1‘).text( formatJson(json) );

// display formatted JSON (from JSON string)
json = ‘{       "a": {         "aa": [             1,            2,            {                 "aaa": "abc",‘+
    ‘                 "bbb": "defgh",                 "ccc": 987             },             [       100,       ‘+
    ‘200,                     300             ,            { "one": 1, "two"  : "ii", "three"  ‘+
    ‘: "Three" }, 1000 ]‘+
    ‘         ],         ‘+
    ‘            "bb":         "xyz",         "ccc": 777     },     "b": [ "qqq", "www", ‘+
    ‘"eee" ],     "c": "hello",     "d": 12345 }‘;
$(‘#formattedJson2‘).text( formatJson(json) );

JS-格式化json