Use fixed size for boundary string, because createBoundary function is private.

Author: octet-stream

lib/Encoder.ts

@@ -66,7 +66,7 @@ export class FormDataEncoder {
    *
    * const encoder = new Encoder(fd)
    */
-  constructor(form: FormDataLike, boundary: string = createBoundary(16)) {
+  constructor(form: FormDataLike, boundary: string = createBoundary()) {
     if (!isFormData(form)) {
       throw new TypeError("Expected first argument to be a FormData instance.")
     }

lib/util/createBoundary.test.ts

@@ -3,20 +3,13 @@ import test from "ava"
 import createBoundary from "./createBoundary"
 
 test("Returns a string", t => {
-  const actual = createBoundary(16)
+  const actual = createBoundary()
 
   t.is(typeof actual, "string")
 })
 
-test("Returns a string of given length", t => {
-  const expected = 24
-  const actual = createBoundary(expected)
-
-  t.is(actual.length, expected)
-})
-
 test("Returns a string that passes regex of valid range", t => {
-  const actual = createBoundary(16)
+  const actual = createBoundary()
 
   t.regex(actual, /^[a-zA-Z0-9'_-]+$/)
 })

lib/util/createBoundary.ts

@@ -3,10 +3,9 @@ const alphabet
 
 /**
  * Generates a boundary string for FormData encoder.
- *
- * @param size The size of the resulting string
  */
-function createBoundary(size: number): string {
+function createBoundary(): string {
+  let size = 16
   let res = ""
 
   while (size--) {