How to Efficiently Iterate Through Nested JSON in Go?

Looping/Iterating Over Second Level Nested JSON in Go Lang

Consider the scenario where you encounter a nested JSON structure like the one depicted below:

{
    "outterJSON": {
        "innerJSON1": {
            "value1": 10,
            "value2": 22,
            "InnerInnerArray": [ "test1" , "test2"],
            "InnerInnerJSONArray": [ {"fld1" : "val1"} , {"fld2" : "val2"} ]
        },
        "InnerJSON2":"NoneValue"
    }
}

The task is to effectively iterate through this structure and retrieve all key-value pairs as strings for further processing. Unfortunately, manually defining a struct for such a dynamic JSON input is not feasible.

Efficient Iteration Approach

To navigate this challenge efficiently, a recursive approach is employed:

func parseMap(m map[string]interface{}) {
  for key, val := range m {
    // Check the type of the value
    switch concreteVal := val.(type) {
      case map[string]interface{}:
        // If it's a nested map, recursively call the function
        parseMap(val.(map[string]interface{}))
      case []interface{}:
        // If it's a nested array, call the function to parse the array
        parseArray(val.([]interface{}))
      default:
        // For all other types, print the key and value as a string
        fmt.Println(key, ":", concreteVal)
    }
  }
}

This recursive function parseMap examines the type of each value in the map. If the value is itself a map, it recursively calls parseMap to traverse that nested map. If the value is an array, it calls parseArray to iterate over it. For all other types (such as strings, numbers, etc.), it simply prints the key and value as a string.

Demo

Consider the example JSON input provided earlier. Running the code below will produce the following output:

func parseArray(a []interface{}) {
  for i, val := range a {
    // Check the type of the value
    switch concreteVal := val.(type) {
      case map[string]interface{}:
        // If it's a nested map, recursively call the function
        parseMap(val.(map[string]interface{}))
      case []interface{}:
        // If it's a nested array, call the function to parse the array
        parseArray(val.([]interface{}))
      default:
        // For all other types, print the index and value as a string
        fmt.Println("Index:", i, ":", concreteVal)
    }
  }
}

const input = `
{
    "outterJSON": {
        "innerJSON1": {
            "value1": 10,
            "value2": 22,
            "InnerInnerArray": [ "test1" , "test2"],
            "InnerInnerJSONArray": [{"fld1" : "val1"} , {"fld2" : "val2"}]
        },
        "InnerJSON2":"NoneValue"
    }
}
`

Output:

//outterJSON
//innerJSON1
//InnerInnerJSONArray
//Index: 0
//fld1 : val1
//Index: 1
//fld2 : val2
//value1 : 10
//value2 : 22
//InnerInnerArray
//Index 0 : test1
//Index 1 : test2
//InnerJSON2 : NoneValue

This approach effectively captures all key-value pairs within the nested JSON, making it suitable for processing and extraction tasks in Go lang.

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