toFormData helper function (axios#3757)

* adding toFormData test

* adding toFormData

Co-authored-by: Jay <jasonsaayman@gmail.com>

lib/helpers/toFormData.js

@@ -0,0 +1,55 @@
+'use strict';
+
+function combinedKey(parentKey, elKey) {
+  return parentKey + '.' + elKey;
+}
+
+function buildFormData(formData, data, parentKey) {
+  if (Array.isArray(data)) {
+    data.forEach(function buildArray(el, i) {
+      buildFormData(formData, el, combinedKey(parentKey, i));
+    });
+  } else if (
+    typeof data === 'object' &&
+    !(data instanceof File || data === null)
+  ) {
+    Object.keys(data).forEach(function buildObject(key) {
+      buildFormData(
+        formData,
+        data[key],
+        parentKey ? combinedKey(parentKey, key) : key
+      );
+    });
+  } else {
+    if (data === undefined) {
+      return;
+    }
+
+    var value =
+      typeof data === 'boolean' || typeof data === 'number'
+        ? data.toString()
+        : data;
+    formData.append(parentKey, value);
+  }
+}
+
+/**
+ * convert a data object to FormData
+ *
+ * type FormDataPrimitive = string | Blob | number | boolean
+ * interface FormDataNest {
+ *   [x: string]: FormVal
+ * }
+ *
+ * type FormVal = FormDataNest | FormDataPrimitive
+ *
+ * @param {FormVal} data
+ */
+
+module.exports = function getFormData(data) {
+  var formData = new FormData();
+
+  buildFormData(formData, data);
+
+  return formData;
+};

test/specs/helpers/toFormData.spec.js

@@ -0,0 +1,18 @@
+var toFormData = require("../../../lib/helpers/toFormData");
+
+describe("toFormData", function () {
+  it("Convert nested data object to FormDAta", function () {
+    var o = {
+      val: 123,
+      nested: {
+        arr: ["hello", "world"],
+      },
+    };
+
+    convertedVal = toFormData(o);
+    expect(convertedVal instanceof FormData).toEqual(true);
+    expect(Array.from(convertedVal.keys()).length).toEqual(3);
+    expect(convertedVal.get("val")).toEqual("123")
+    expect(convertedVal.get("nested.arr.0")).toEqual("hello")
+  });
+});