forked from zhurui/management
210 lines
4.1 KiB
Markdown
210 lines
4.1 KiB
Markdown
# traverse
|
|
|
|
Traverse and transform objects by visiting every node on a recursive walk.
|
|
|
|
[](http://ci.testling.com/substack/js-traverse)
|
|
|
|
[](http://travis-ci.org/substack/js-traverse)
|
|
|
|
# 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 ]
|
|
|
|
## scrub circular references
|
|
|
|
scrub.js:
|
|
|
|
````javascript
|
|
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](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.
|
|
|
|
## .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](http://npmjs.org) do:
|
|
|
|
$ npm install traverse
|
|
|
|
# license
|
|
|
|
MIT
|