Display nested JSON in HTML Dropdowns dynamically

Question

I have been breaking my head with adding the below functionality in UI using HTML5 BOOTSTRAP-CSS-JS.

I am trying to create UI Dropdowns by consuming JSON input.

NOTE: The "JSON keys" are also to be consumed as dropdowns values rather than just the general "JSON values".. hence, i am unable to work out a logic for the same!

I have JSONs in the exact below format:

{
  "BIKE LIST": {
    "Bajaj": {
      "Pulsar": {
        "350 CC": [
          "2019 Model",
          "2020 Model"
        ],
        "500 CC": [
          "2018 Model",
          "2021 Model"
        ]
      }
    }
  },
  "CAR LIST": {
    "Toyota": {
      "Etios": {
        "Liva": [
          "2019 Model",
          "2020 Model"
        ],
        "Regular": [
          "2018 Model",
          "2021 Model"
        ]
      }
    },
  }
}

I would like to create 5 DYNAMIC dropdowns in UI as follows:

Dropdown 1 values: BIKE LIST, CAR LIST

Dropdown 2 ( values displayed according to user selection in Dropdown 1): i.e. if User selects BIKE LIST, I should have "Bajaj"

Dropdown 3 ( values displayed according to user selection in Dropdown 2): i.e. if User selects Bajaj, I should have "Pulsar"

Dropdown 4 ( values displayed according to user selection in Dropdown 3): i.e. if User selects Pulsar, I should have "350 CC", "500 CC"

Dropdown 5 ( values displayed according to user selection in Dropdown 4): i.e. if User selects 500 CC, I should have "2018 Model", "2021 Model"

Doan Van Thang · Accepted Answer · 2021-02-09 14:01:36Z

I tried to make it clean as possible

const input = {
    "BIKE LIST": {
        "Bajaj": {
            "Pulsar": {
                "350 CC": [
                    "2019 Model",
                    "2020 Model"
                ],
                "500 CC": [
                    "2018 Model",
                    "2021 Model"
                ]
            }
        }
    },
    "CAR LIST": {
        "Toyota": {
            "Etios": {
                "Liva": [
                    "2019 Model",
                    "2020 Model"
                ],
                "Regular": [
                    "2018 Model",
                    "2021 Model"
                ]
            }
        },
    }
}

var select1 = document.getElementById("select1");
var select2 = document.getElementById("select2");
var select3 = document.getElementById("select3");
var select4 = document.getElementById("select4");
var select5 = document.getElementById("select5");

function createSelect(params, select_dom) {
    select_dom.innerHTML = "";
    var first_child = null;
    for (const key in params) {
        if (first_child == null) first_child = params[key];
        var option = document.createElement("option");
        if (params.constructor === Array)
            option.text = params[key]
        else
            option.text = key;
        select_dom.add(option);
    }
    return first_child;
}

function initSelect(params, list_dom) {
    var small_input = params;
    for (let index = 0; index < list_dom.length; index++) {
        const element = list_dom[index];
        if (small_input) {
            small_input = createSelect(small_input, element);
        }
    }
}

initSelect(input, [select1, select2, select3, select4, select5])

select1.addEventListener("change", function () {
    initSelect(input[select1.value], [select2, select3, select4, select5])
});
select2.addEventListener("change", function () {
    initSelect(input[select1.value][select2.value], [select3, select4, select5])
});
select3.addEventListener("change", function () {
    initSelect(input[select1.value][select2.value][select3.value], [select4, select5])
});
select4.addEventListener("change", function () {
    initSelect(input[select1.value][select2.value][select3.value][select4.value], [select5])
});

<select id="select1"></select>
<select id="select2"></select>
<select id="select3"></select>
<select id="select4"></select>
<select id="select5"></select>

I see it's like in a cascading dropdown implementation. Thank you mate. Works like a charm !!

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