JSON.prune is a pruning JSON.stringify for the very specific cases where you need to stringify big or recursive javascript objects and don't really need the result to be complete.
var json = JSON.stringify(window); // fails
var json = JSON.prune(window); // builds a JSON valid string from a pruned version of the
// recursive, deep, and not totally accessible window object
var prunedWindow = JSON.parse(JSON.prune(window)); // builds a lighter acyclic version of window
JSON.prune also lets you, in case of need, stringify inherited and/or non enumerable properties.
JSON.prune(window.location, {inheritedProperties:true}); // without inherited properties, FireFox and IE only show an empty object
JSON.prune.log is a proxy over console.log deep cloning the objects (using JSON.prune) before logging them, in order to avoid the delay problem encountered on non primitive objects logging.
You should not use it frequently, only when you really need to see the objects how they were at logging time.
// make sure someObject is logged as it was at logging time
JSON.prune.log(someObject);
<script src=http://dystroy.org/JSON.prune/JSON.prune.js></script>
var prune = require('json-prune');
var json = prune(obj);
Here's how are handled by default by JSON.prune the special values needing pruning:
| Value | Default |
|---|---|
undefined |
Key and value are ommited (same as JSON.stringify) |
| function | Key and value are ommited (same as JSON.stringify) |
| already written or too deep object (cycle prevention) | The "-pruned-" string |
| array with too many elements | Truncation: JSON.prune applied to only the start of the array |
By specifiying a replacer or a prunedString in JSON.prune options, you can customize those prunings.
The replacer function takes 3 arguments:
- the value to replace
- the default replacement value
- a boolean indicating whether the replacement is due to a cycle detection
Returning undefined makes JSON.prune ommit the property (name and value).
The default value makes it easy to just specify the specific behavior you want instead of implementing the whole standard replacement.
var json = JSON.prune(obj, {prunedString: '{}' });
Note: if you want a string to be inserted, don't forget the double quotes, as in '"-pruned-"'.
If you want the pruned properties to just be ommited, pass undefined as prunedString:
var obj = {a:3};
obj.self = obj;
var json = JSON.prune(obj);
console.log(json); // logs {"a":3,"self":"-pruned-"}
json = JSON.prune(obj, {prunedString: undefined });
console.log(json); // logs {"a":3}
Note: You get the same behavior with
json = JSON.prune(obj, {replacer: function(){}});
var options = {replacer:function(value, defaultValue, circular){
if (circular) return '"-circular-"';
if (value === undefined) return '"-undefined-"';
if (Array.isArray(value)) return '"-array('+value.length+')-"';
return defaultValue;
}};
var json = JSON.prune(obj, options);
var options = {replacer:function(value, defaultValue){
if (typeof value === "function") return JSON.stringify(value.toString());
return defaultValue;
}};
var json = JSON.prune(obj, options);
The default behavior on big arrays is to silently write only the first elements. It's possible with a replacer to add a string as last element:
var obj = {arr: Array.apply(0,Array(100)).map(function(_,i){ return i+1 })}
function replacer(value, defaultValue){
if (Array.isArray(value)) return defaultValue.replace(/]$/, ',"-truncated-"]');
return defaultValue;
}
var json = (asPrunedJSON(obj, {arrayMaxLength:5, replacer});
This produces
{"arr":[1,2,3,4,5,"-truncated-"]}
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