Recurse JavaScript Object to Get Values for a Given Key the Easy Way

I had a scenario where I needed to find values for a key in a complex JavaScript object which could be nested n levels deep.

I found numerous approaches to doing this, most were overly complicated, so I thought I would share the most straightforward, concise process.

the Code

You can do this in a straightforward function implementing the "tail call recursion" pattern to search for a key (key) from the root of an object (obj), excluding any keys in excludeKeys.

This will return a list of values for the given key, searching all levels in all branches of the object.

function getAllValuesForKey(obj, key, excludeKeys=[], values=[]) {
    for (let k in obj) {
        if (typeof obj[k] === "object") {
            if(!excludeKeys.includes(k)){
                getAllValuesForKey(obj[k], key, excludeKeys, values)
            }
        } else {
            if (k === key){
                values.push(obj[k]);
            }
        }
    }
    return values;
}

Example

In parsing an OpenAPI or Swagger specification, I am looking for all of the schema refs in a successful response body, for example:

paths:
    '/orgs/{org}/actions/permissions/selected-actions':
        get:
          ...
          responses:
            '200': '...'

however these refs can present in various different ways depending upon the response type, such as:

'200':
    $ref: '#/components/responses/actions_runner_labels'

or

'200':      
    content:
        application/json:
          schema:
            $ref: '#/components/schemas/runner'

or

'200':
  content:
    application/json:
      schema:
        anyOf:
          - $ref: '#/components/schemas/interaction-limit-response'

or

'200':
  content:
    application/json:
      schema:
        type: object
        required:
          - total_count
          - runners
        properties:
          total_count:
            type: integer
          runners:
            type: array
            items:
              $ref: '#/components/schemas/runner'

To find all of the schema refs without knowing the response type or structure I used the above function as follows (excluding refs for examples):

function getRespSchemaName(op){
    for(let respCode in op.responses){
        if(respCode.startsWith('2')){
            return getAllValuesForKey(op.responses[respCode], "$ref", ['examples']);
        }
    }
}

You can find this implementation in openapi-doc-util and @stackql/openapi-doc-util.

simple!

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