Converting multiline, indented json to single line using javascript

Question

I've come up with the following function for converting a multiline, nicely indented json to a single line

function(text) {
    var outerRX = /((?:".*?")|(\s|\n|\r)+)/g,
        innerRX = /^(\s|\n|\r)+$/;

    return text.replace(outerRX, function($0, $1) {
        return $1.match(innerRX) ? "" : $1 ;
    });
}

Can anyone come up with something better, both in terms of efficiency and fixing bugs that exist in my implementation (e.g. mine breaks when parsing

{
    "property":"is dangerously
             spaced out" 
}

or

{
    "property":"is dangerously \" punctuated" 
}

Are you attempting to minify the JSON? There are open source solutions that exist for this. — Jason McCreary
– Jason McCreary, Commented Apr 26, 2011 at 13:54
Ideally, yes, it would be minified server side, but no-one here has the time to do that right now, so I have to have an easily maintainable (i.e. indented, multiline) json file that gets passed exactly as is to jQuery.ajax — wheresrhys
– wheresrhys, Commented Apr 26, 2011 at 13:58
Have you looked at jsmin? There are both server side and client side versions you can use. — awm
– awm, Commented Apr 26, 2011 at 14:23
The trouble with jsmin is that it minifies javascript, but json is only a subset of javascript, so I bet it runs a whole load of regex that aren't needed in this case. So while it's undoubtedly less buggy than my function, it's probably less efficient than a non-buggy, single-purpose json minifying function would be. Also, I'm not sure the link you posted above for a client-side version is client-side - all I can find there are links to C and .exe files - both server side — wheresrhys
– wheresrhys, Commented Apr 26, 2011 at 14:35

jmbucknall · Accepted Answer · 2011-04-26 17:47:03Z

2

For this kind of problem, I follow the adage that adding regex just gives you two problems. It's a simple enough parsing problem, so here's a parsing solution:

var minifyJson = function (inJson) {
  var outJson, // the output string
      ch,      // the current character
      at,      // where we're at in the input string
      advance = function () {
        at += 1;
        ch = inJson.charAt(at);
      },
      skipWhite = function () {
        do { advance(); } while (ch && (ch <= ' '));
      },
      append = function () {
        outJson += ch;
      },
      copyString = function () {
        while (true) {
          advance();
          append();
          if (!ch || (ch === '"')) {
            return;
          }
          if (ch === '\\') {
            advance();
            append();
          }
        }
      },
      initialize = function () {
        outJson = "";
        at = -1;
      };

  initialize();
  skipWhite();

  while (ch) {
    append();
    if (ch === '"') {
      copyString();
    }
    skipWhite();
  }
  return outJson;
};

Note that the code does not have any error-checking to see if the JSON is properly formed. The only error (no closing quotes for a string) is ignored.

answered Apr 26, 2011 at 17:47

jmbucknall

2,06113 silver badges14 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

wheresrhys Over a year ago

I'm very reluctant to admit defeat using regex, but have found that javascript regex's lack of support for lookbehind is a real hindrance, so I'm going to try your approach - thanks very much for sharing it.

wheresrhys · Accepted Answer · 2011-04-26 14:59:11Z

0

This fixes the two bugs in the question, but probably not very efficiently

function(text) {
    var outerRX = /((?:"([^"]|(\\"))*?(?!\\)")|(\s|\n|\r)+)/g,
    innerRX = /^(\s|\n|\r)+$/;

    return text.replace(outerRX, function($0, $1) {
        return $1.match(/^(\s|\n|\r)+$/) ? "" : $1 ;
    });
}

answered Apr 26, 2011 at 14:59

wheresrhys

23.7k21 gold badges97 silver badges165 bronze badges

Collectives™ on Stack Overflow

Converting multiline, indented json to single line using javascript

2 Answers 2

1 Comment

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related