diff --git a/lib/helpers/toFormData.js b/lib/helpers/toFormData.js
index 6dcb9d2..307b86f 100644
--- a/lib/helpers/toFormData.js
+++ b/lib/helpers/toFormData.js
@@ -4,14 +4,37 @@ var utils = require('../utils');
 var AxiosError = require('../core/AxiosError');
 var envFormData = require('../env/classes/FormData');
 
+/**
+ * Determines if the given thing is a array or js object.
+ *
+ * @param {string} thing - The object or array to be visited.
+ *
+ * @returns {boolean}
+ */
 function isVisitable(thing) {
   return utils.isPlainObject(thing) || utils.isArray(thing);
 }
 
+/**
+ * It removes the brackets from the end of a string
+ *
+ * @param {string} key - The key of the parameter.
+ *
+ * @returns {string} the key without the brackets.
+ */
 function removeBrackets(key) {
   return utils.endsWith(key, '[]') ? key.slice(0, -2) : key;
 }
 
+/**
+ * It takes a path, a key, and a boolean, and returns a string
+ *
+ * @param {string} path - The path to the current key.
+ * @param {string} key - The key of the current object being iterated over.
+ * @param {string} dots - If true, the key will be rendered with dots instead of brackets.
+ *
+ * @returns {string} The path to the current key.
+ */
 function renderKey(path, key, dots) {
   if (!path) return key;
   return path.concat(key).map(function each(token, i) {
@@ -21,6 +44,13 @@ function renderKey(path, key, dots) {
   }).join(dots ? '.' : '');
 }
 
+/**
+ * If the array is an array and none of its elements are visitable, then it's a flat array.
+ *
+ * @param {Array<any>} arr - The array to check
+ *
+ * @returns {boolean}
+ */
 function isFlatArray(arr) {
   return utils.isArray(arr) && !arr.some(isVisitable);
 }
@@ -29,12 +59,20 @@ var predicates = utils.toFlatObject(utils, {}, null, function filter(prop) {
   return /^is[A-Z]/.test(prop);
 });
 
+/**
+ * If the thing is a FormData object, return true, otherwise return false.
+ *
+ * @param {unknown} thing - The thing to check.
+ *
+ * @returns {boolean}
+ */
 function isSpecCompliant(thing) {
   return thing && utils.isFunction(thing.append) && thing[Symbol.toStringTag] === 'FormData' && thing[Symbol.iterator];
 }
 
 /**
  * Convert a data object to FormData
+ *
  * @param {Object} obj
  * @param {?Object} [formData]
  * @param {?Object} [options]
@@ -42,9 +80,19 @@ function isSpecCompliant(thing) {
  * @param {Boolean} [options.metaTokens = true]
  * @param {Boolean} [options.dots = false]
  * @param {?Boolean} [options.indexes = false]
+ *
  * @returns {Object}
  **/
 
+/**
+ * It converts an object into a FormData object
+ *
+ * @param {Object<any, any>} obj - The object to convert to form data.
+ * @param {string} formData - The FormData object to append to.
+ * @param {Object<string, any>} options
+ *
+ * @returns
+ */
 function toFormData(obj, formData, options) {
   if (!utils.isObject(obj)) {
     throw new TypeError('target must be an object');
@@ -94,11 +142,13 @@ function toFormData(obj, formData, options) {
   }
 
   /**
+   * Default visitor.
    *
    * @param {*} value
    * @param {String|Number} key
    * @param {Array<String|Number>} path
    * @this {FormData}
+   *
    * @returns {boolean} return true to visit the each prop of the value recursively
    */
   function defaultVisitor(value, key, path) {