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