I did what I initially feared I'll have to do : I took Crockford's code and modified it for my needs. Now it builds JSON but handles

• cycles


• too deep objects


• too long arrays


• exceptions (accessors that can't legally be accessed)

In case anybody needs it, I made a GitHub repository : JSON.prune on GitHub

Here is the code :

// JSON.pruned : a function to stringify any object without overflow

// example : var json = JSON.pruned({a:'e', c:[1,2,{d:{e:42, f:'deep'}}]})

// two additional optional parameters :

//   - the maximal depth (default : 6)

//   - the maximal length of arrays (default : 50)

// GitHub : https://github.com/Canop/JSON.prune

// This is based on Douglas Crockford's code ( https://github.com/douglascrockford/JSON-js/blob/master/json2.js )

(function () {

    'use strict';



    var DEFAULT_MAX_DEPTH = 6;

    var DEFAULT_ARRAY_MAX_LENGTH = 50;

    var seen; // Same variable used for all stringifications



    Date.prototype.toPrunedJSON = Date.prototype.toJSON;

    String.prototype.toPrunedJSON = String.prototype.toJSON;



    var cx = /[u0000u00adu0600-u0604u070fu17b4u17b5u200c-u200fu2028-u202fu2060-u206fufeffufff0-uffff]/g,

        escapable = /[\\x00-x1fx7f-x9fu00adu0600-u0604u070fu17b4u17b5u200c-u200fu2028-u202fu2060-u206fufeffufff0-uffff]/g,

        meta = {    // table of character substitutions

            'b': '\b',

            't': '\t',

            'n': '\n',

            'f': '\f',

            'r': '\r',

            '' : '\',

            '\': '\\'

        };



    function quote(string) {

        escapable.lastIndex = 0;

        return escapable.test(string) ? '' + string.replace(escapable, function (a) {

            var c = meta[a];

            return typeof c === 'string'

                ? c

                : '\u' + ('0000' + a.charCodeAt(0).toString(16)).slice(-4);

        }) + '' : '' + string + '';

    }



    function str(key, holder, depthDecr, arrayMaxLength) {

        var i,          // The loop counter.

            k,          // The member key.

            v,          // The member value.

            length,

            partial,

            value = holder[key];

        if (value && typeof value === 'object' && typeof value.toPrunedJSON === 'function') {

            value = value.toPrunedJSON(key);

        }



        switch (typeof value) {

        case 'string':

            return quote(value);

        case 'number':

            return isFinite(value) ? String(value) : 'null';

        case 'boolean':

        case 'null':

            return String(value);

        case 'object':

            if (!value) {

                return 'null';

            }

            if (depthDecr<=0 || seen.indexOf(value)!==-1) {

                return '-pruned-';

            }

            seen.push(value);

            partial = [];

            if (Object.prototype.toString.apply(value) === '[object Array]') {

                length = Math.min(value.length, arrayMaxLength);

                for (i = 0; i < length; i += 1) {

                    partial[i] = str(i, value, depthDecr-1, arrayMaxLength) || 'null';

                }

                v = partial.length === 0

                    ? '[]'

                    : '[' + partial.join(',') + ']';

                return v;

            }

            for (k in value) {

                if (Object.prototype.hasOwnProperty.call(value, k)) {

                    try {

                        v = str(k, value, depthDecr-1, arrayMaxLength);

                        if (v) partial.push(quote(k) + ':' + v);

                    } catch (e) { 

                        // this try/catch due to some Accessing selectionEnd on an input element that cannot have a selection. on Chrome

                    }

                }

            }

            v = partial.length === 0

                ? '{}'

                : '{' + partial.join(',') + '}';

            return v;

        }

    }



    JSON.pruned = function (value, depthDecr, arrayMaxLength) {

        seen = [];

        depthDecr = depthDecr || DEFAULT_MAX_DEPTH;

        arrayMaxLength = arrayMaxLength || DEFAULT_ARRAY_MAX_LENGTH;

        return str('', {'': value}, depthDecr, arrayMaxLength);

    };



}());

An example of what can be done :

var json = JSON.pruned(window);

Note: Contrary to the code in this answer, the GitHub repository is updated when needed (documentation, compatibility, use as module in commonjs or node, specific serializations, etc.). It's a good idea to start from the repository if you need this pruning feature.