traverse

traverse and transform objects by visiting every node on a recursive walk

``npm install traverse``

traverse

Traverse and transform objects by visiting every node on a recursive walk.

examples

transform negative numbers in-place

negative.js

``````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

``````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 ]
``````

scrub circular references

scrub.js:

``````var traverse = require('traverse');

var obj = { a : 1, b : 2, c : [ 3, 4 ] };
obj.c.push(obj);

var scrubbed = traverse(obj).map(function (x) {
if (this.circular) this.remove()
});
console.dir(scrubbed);
``````

output:

``````{ a: 1, b: 2, c: [ 3, 4 ] }
``````

methods

Each method that takes an `fn` uses the context documented below in the context section.

.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) 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.

.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.

.get(path)

Get the element at the array `path`.

.set(path, value)

Set the element at the array `path` to `value`.

.has(path)

Return whether the element at the array `path` exists.

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, stopHere=false)

Set a new value for the present node.

All the elements in `value` will be recursively traversed unless `stopHere` is true.

this.remove(stopHere=false)

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(stopHere=false)

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.

You can assign into `this.keys` here to traverse in a custom order.

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.

install

Using npm do:

``````\$ npm install traverse
``````