Traversing over an object in node.js
Sometimes I get into a situation in which I may want to loop over all the nodes of a given object. That is I want to traverse, or loop over an object and preform a certain action with certain key value pairs of an object that has one or more nested objects in it.
I could slap together my own solution for looping over all nested object keys, maybe starting with a for in loop that I use in a method that is called recursively. However a much better option would likely be to just go ahead and use traverse as this seems to work just fine for this kind of task.
1 - Install the traverse npm package
You know the deal whe it comes to adding an npm package to a stack, unless you do not in which case.
This will install traverse into the current project folder and save it as a dependency of the project in the package.json file.
2 - The Object
So just for the sake of this post I will be starting with the following code for each example.
Each following example will be code that is written after the above code. Notice that the object has a nested object within yet another nested object, in addition to having some primitive key values also (String, Boolean, and Number). Although this is a silly example object, in the wild I come across objects like this all the time, and sometimes I would like to walk over them for one reason or another.
3 - forEach example
So I thought I would start off with a simple forEach example.
So this works a whole lot like Array.forEach in that it loops over each key value pare of the Object. As you would expect it does not work just the same way because I am looping over just a plain old object rather than an instance of Array. Also via the use of the this keyword I have access to a whole lot of helpful properties when walking over the object such as this.path, also this.node can be used as an alternative to the node argument.
3 - Paths example
So there are a lot of useful methods in this dependency that help with what comes to mind when dealing with this certain aspect of node.js development. The Path method for example will return an array of all possible paths in the object which I am sure will come in handy now and then.
4 - reduce example
Okay now for an example using the reduce method, this should be fun.
Reduce can be used to return a new object that is constructed during the process of looping over the contents on the object. Here I am creating a new object that only has the structure of my foo object that contains keys that have numbers.
5 - Conclusion
So the the traverse npm package is a good way to go about looping over all the contents of an object in a nodejs project. Although it looks like it is not supported any more, so maybe another solution should be looked into on this one. It is true that just because a project is not being supported it does not mean that it is broken, there is a difference between supporting and mangling.
Be sure to check out my many other posts on node.js and npm packages.