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- # traverse <sup>[![Version Badge][npm-version-svg]][package-url]</sup>
- [![github actions][actions-image]][actions-url]
- [![coverage][codecov-image]][codecov-url]
- [![License][license-image]][license-url]
- [![Downloads][downloads-image]][downloads-url]
- [![npm badge][npm-badge-png]][package-url]
- 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 ]
- ## 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
- [package-url]: https://npmjs.org/package/traverse
- [npm-version-svg]: https://versionbadg.es/ljharb/traverse.svg
- [deps-svg]: https://david-dm.org/ljharb/traverse.svg
- [deps-url]: https://david-dm.org/ljharb/traverse
- [dev-deps-svg]: https://david-dm.org/ljharb/traverse/dev-status.svg
- [dev-deps-url]: https://david-dm.org/ljharb/traverse#info=devDependencies
- [npm-badge-png]: https://nodei.co/npm/traverse.png?downloads=true&stars=true
- [license-image]: https://img.shields.io/npm/l/traverse.svg
- [license-url]: LICENSE
- [downloads-image]: https://img.shields.io/npm/dm/traverse.svg
- [downloads-url]: https://npm-stat.com/charts.html?package=traverse
- [codecov-image]: https://codecov.io/gh/ljharb/traverse/branch/main/graphs/badge.svg
- [codecov-url]: https://app.codecov.io/gh/ljharb/traverse/
- [actions-image]: https://img.shields.io/endpoint?url=https://github-actions-badge-u3jn4tfpocch.runkit.sh/ljharb/traverse
- [actions-url]: https://github.com/ljharb/traverse/actions
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