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traverse
========
Traverse and transform objects by visiting every node on a recursive walk.
examples
========
transform negative numbers in-place
-----------------------------------
negative.js
````javascript
var traverse = require('traverse');
var obj = [ 5, 6, -3, [ 7, 8, -2, 1 ], { f : 10, g : -13 } ];
traverse(obj).forEach(function (x) {
if (x < 0) this.update(x + 128);
});
console.dir(obj);
````
Output:
[ 5, 6, 125, [ 7, 8, 126, 1 ], { f: 10, g: 115 } ]
collect leaf nodes
------------------
leaves.js
````javascript
var traverse = require('traverse');
var obj = {
a : [1,2,3],
b : 4,
c : [5,6],
d : { e : [7,8], f : 9 },
};
var leaves = traverse(obj).reduce(function (acc, x) {
if (this.isLeaf) acc.push(x);
return acc;
}, []);
console.dir(leaves);
````
Output:
[ 1, 2, 3, 4, 5, 6, 7, 8, 9 ]
context
=======
Each method that takes a callback has a context (its `this` object) with these
attributes:
this.node
---------
The present node on the recursive walk
this.path
---------
An array of string keys from the root to the present node
this.parent
-----------
The context of the node's parent.
This is `undefined` for the root node.
this.key
--------
The name of the key of the present node in its parent.
This is `undefined` for the root node.
this.isRoot, this.notRoot
-------------------------
Whether the present node is the root node
this.isLeaf, this.notLeaf
-------------------------
Whether or not the present node is a leaf node (has no children)
this.level
----------
Depth of the node within the traversal
this.circular
-------------
If the node equals one of its parents, the `circular` attribute is set to the
context of that parent and the traversal progresses no deeper.
this.update(value)
------------------
Set a new value for the present node.
this.remove()
-------------
Remove the current element from the output. If the node is in an Array it will
be spliced off. Otherwise it will be deleted from its parent.
this.delete()
-------------
Delete the current element from its parent in the output. Calls `delete` even on
Arrays.
this.before(fn)
---------------
Call this function before any of the children are traversed.
this.after(fn)
--------------
Call this function after any of the children are traversed.
this.pre(fn)
------------
Call this function before each of the children are traversed.
this.post(fn)
-------------
Call this function after each of the children are traversed.
methods
=======
.map(fn)
--------
Execute `fn` for each node in the object and return a new object with the
results of the walk. To update nodes in the result use `this.update(value)`.
.forEach(fn)
------------
Execute `fn` for each node in the object but unlike `.map()`, when
`this.update()` is called it updates the object in-place.
.reduce(fn, acc)
----------------
For each node in the object, perform a
[left-fold](http://en.wikipedia.org/wiki/Fold_(higher-order_function))
with the return value of `fn(acc, node)`.
If `acc` isn't specified, `acc` is set to the root object for the first step
and the root element is skipped.
.deepEqual(obj)
---------------
Returns a boolean, whether the instance value is equal to the supplied object
along a deep traversal using some opinionated choices.
Some notes:
* RegExps are equal if their .toString()s match, but not functions since
functions can close over different variables.
* Date instances are compared using `.getTime()` just like `assert.deepEqual()`.
* Circular references must refer to the same paths within the data structure for
both objects. For instance, in this snippet:
````javascript
var a = [1];
a.push(a); // a = [ 1, *a ]
var b = [1];
b.push(a); // b = [ 1, [ 1, *a ] ]
````
`a` is not the same as `b` since even though the expansion is the same, the
circular references in each refer to different paths into the data structure.
However, in:
````javascript
var c = [1];
c.push(c); // c = [ 1, *c ];
````
`c` is equal to `a` in a `deepEqual()` because they have the same terminal node
structure.
* Arguments objects are not arrays and neither are they the same as regular
objects.
* Instances created with `new` of String, Boolean, and Number types are never
equal to the native versions.
.paths()
--------
Return an `Array` of every possible non-cyclic path in the object.
Paths are `Array`s of string keys.
.nodes()
--------
Return an `Array` of every node in the object.
.clone()
--------
Create a deep clone of the object.
installation
============
Using npm:
npm install traverse
Or check out the repository and link your development copy:
git clone http://github.com/substack/js-traverse.git
cd js-traverse
npm link .
You can test traverse with "expresso":http://github.com/visionmedia/expresso
(`npm install expresso`):
js-traverse $ expresso
100% wahoo, your stuff is not broken!
hash transforms
===============
This library formerly had a hash transformation component. It has been
[moved to the hashish package](https://github.com/substack/node-hashish).