refactor(binary): reduce code dupe, remove invalid branches

Author: mbroadst

lib/binary.js

@@ -27,27 +27,19 @@ class Binary {
       !(buffer instanceof Uint8Array) &&
       !Array.isArray(buffer)
     ) {
-      throw new Error('only String, Buffer, Uint8Array or Array accepted');
+      throw new TypeError('only String, Buffer, Uint8Array or Array accepted');
     }
 
-    if (buffer instanceof Number) {
-      this.sub_type = buffer;
-      this.position = 0;
-    } else {
-      this.sub_type = subType == null ? BSON_BINARY_SUBTYPE_DEFAULT : subType;
-      this.position = 0;
-    }
+    this.sub_type = subType == null ? BSON_BINARY_SUBTYPE_DEFAULT : subType;
+    this.position = 0;
 
     if (buffer != null && !(buffer instanceof Number)) {
       // Only accept Buffer, Uint8Array or Arrays
       if (typeof buffer === 'string') {
         // Different ways of writing the length of the string for the different types
         if (typeof Buffer !== 'undefined') {
           this.buffer = new Buffer(buffer);
-        } else if (
-          typeof Uint8Array !== 'undefined' ||
-          Object.prototype.toString.call(buffer) === '[object Array]'
-        ) {
+        } else if (typeof Uint8Array !== 'undefined' || Array.isArray(buffer)) {
           this.buffer = writeStringToArray(buffer);
         } else {
           throw new TypeError('only String, Buffer, Uint8Array or Array accepted');
@@ -64,8 +56,6 @@ class Binary {
       } else {
         this.buffer = new Array(Binary.BUFFER_SIZE);
       }
-      // Set position to start of buffer
-      this.position = 0;
     }
   }
 
@@ -105,7 +95,7 @@ class Binary {
       } else {
         let buffer = null;
         // Create a new buffer (typed or normal array)
-        if (Object.prototype.toString.call(this.buffer) === '[object Uint8Array]') {
+        if (isUint8Array(this.buffer)) {
           buffer = new Uint8Array(new ArrayBuffer(Binary.BUFFER_SIZE + this.buffer.length));
         } else {
           buffer = new Array(Binary.BUFFER_SIZE + this.buffer.length);
@@ -142,7 +132,7 @@ class Binary {
       if (typeof Buffer !== 'undefined' && Buffer.isBuffer(this.buffer)) {
         buffer = new Buffer(this.buffer.length + string.length);
         this.buffer.copy(buffer, 0, 0, this.buffer.length);
-      } else if (Object.prototype.toString.call(this.buffer) === '[object Uint8Array]') {
+      } else if (isUint8Array(this.buffer)) {
         // Create a new buffer
         buffer = new Uint8Array(new ArrayBuffer(this.buffer.length + string.length));
         // Copy the content
@@ -169,10 +159,7 @@ class Binary {
       this.position =
         offset + string.length > this.position ? offset + string.length : this.position;
       // offset = string.length;
-    } else if (
-      Object.prototype.toString.call(string) === '[object Uint8Array]' ||
-      (Object.prototype.toString.call(string) === '[object Array]' && typeof string !== 'string')
-    ) {
+    } else if (isUint8Array(string) || (Array.isArray(string) && typeof string !== 'string')) {
       for (let i = 0; i < string.length; i++) {
         this.buffer[offset++] = string[i];
       }
@@ -246,10 +233,9 @@ class Binary {
           return this.buffer.slice(0, this.position);
         } else {
           // Create a new buffer to copy content to
-          const newBuffer =
-            Object.prototype.toString.call(this.buffer) === '[object Uint8Array]'
-              ? new Uint8Array(new ArrayBuffer(this.position))
-              : new Array(this.position);
+          const newBuffer = isUint8Array(this.buffer)
+            ? new Uint8Array(new ArrayBuffer(this.position))
+            : new Array(this.position);
 
           // Copy content
           for (let i = 0; i < this.position; i++) {
@@ -296,6 +282,10 @@ class Binary {
  */
 const BSON_BINARY_SUBTYPE_DEFAULT = 0;
 
+function isUint8Array(obj) {
+  return Object.prototype.toString.call(obj) === '[object Uint8Array]';
+}
+
 /**
  * @ignore
  */