Remove dependency on is-buffer (#1816)

* Remove dependency on is-buffer from package.json

lib/utils.js

@@ -1,7 +1,6 @@
 'use strict';
 
 var bind = require('./helpers/bind');
-var isBuffer = require('is-buffer');
 
 /*global toString:true*/
 
@@ -19,6 +18,17 @@ function isArray(val) {
   return toString.call(val) === '[object Array]';
 }
 
+
+/**
+ * Determine if a value is a Buffer
+ *
+ * @param {Object} val The value to test
+ * @returns {boolean} True if value is a Buffer, otherwise false
+ */
+function isBuffer(val) {
+  return ![undefined, null].includes(val) && val.constructor === Buffer;
+}
+
 /**
  * Determine if a value is an ArrayBuffer
  *

package.json

@@ -73,8 +73,7 @@
   },
   "typings": "./index.d.ts",
   "dependencies": {
-    "follow-redirects": "1.5.10",
-    "is-buffer": "^2.0.2"
+    "follow-redirects": "^1.4.1"
   },
   "bundlesize": [
     {

test/specs/utils/isX.spec.js

@@ -7,6 +7,12 @@ describe('utils::isX', function () {
     expect(utils.isArray({length: 5})).toEqual(false);
   });
 
+  it('should validate Buffer', function () {
+    expect(utils.isBuffer(Buffer.from('a'))).toEqual(true);
+    expect(utils.isBuffer(null)).toEqual(false);
+    expect(utils.isBuffer(undefined)).toEqual(false);
+  });
+
   it('should validate ArrayBuffer', function () {
     expect(utils.isArrayBuffer(new ArrayBuffer(2))).toEqual(true);
     expect(utils.isArrayBuffer({})).toEqual(false);