Javascript filter array throwing errors and crashing
<p>I am writing a mobile app based on NativeScript, in Typescript/ JavaScript. This snippet of code is called after a Bluetooth scan has been completed. I need to find the correct service. My code works up until I try to select the service I want from the options. The <code>services.filter(function (obj) {</code> line seems to be causing the app to crash, but the error log doesn't make much sense to me...</p>

<pre><code>console.log("Connect Variable");
var services: Array&lt;string&gt;;
var service: any;
services = []; //initialise array
bluetooth.connect(
    {
     UUID: _peripheral.UUID,
     // NOTE: we could just use the promise as this cb is only invoked once
        onConnected: function (peripheral) {
            console.log("------- Peripheral connected: " + JSON.stringify(peripheral));
            // Put all Services into an Array
            peripheral.services.forEach(function (value) {
                console.log("---- ###### adding service: " + value.UUID);
                services.push(value);
            });

            //search for the correct service
            service = peripheral.services.filter(function (obj) { // &lt;- PROBLEM LINE ****************** Caudsing the app to crash out ...
                return obj.UUID == 'A000';
            });
        },
    }
);
</code></pre>

<p>Here is the console log:</p>

<pre><code>CONSOLE LOG file:///app/Pages/Home/home.component.js:145:32: ---- ###### adding service: A000
CONSOLE LOG file:///app/Pages/Home/home.component.js:145:32: ---- ###### adding service: 180A
***** Fatal JavaScript exception - application has been terminated. *****
Native stack trace:
1   0xbea99 NativeScript::FFICallback&lt;NativeScript::ObjCMethodCallback&gt;::ffiClosureCallback(ffi_cif*, void*, void**, void*)
2   0x4ae381 ffi_closure_inner_SYSV
3   0x4b20b8 ffi_closure_SYSV
4   0x25e59d15 &lt;redacted&gt;
5   0x25e59e4b &lt;redacted&gt;
6   0x25e5f9f3 &lt;redacted&gt;
7   0x208d1823 &lt;redacted&gt;
8   0x208d180f &lt;redacted&gt;
9   0x208dfba9 &lt;redacted&gt;
10  0x20d25bdd &lt;redacted&gt;
11  0x20d240d7 &lt;redacted&gt;
12  0x20c732e9 CFRunLoopRunSpecific
13  0x20c730d5 CFRunLoopRunInMode
14  0x22263ac9 GSEventRunModal
15  0x253380b9 UIApplicationMain
16  0x4b202c ffi_call_SYSV
17  0x4ae0c3 ffi_call
18  0x91a0b NativeScript::FFICall::call(JSC::ExecState*)
19  0x2e4931 JSC::LLInt::setUpCall(JSC::ExecState*, JSC::Instruction*, JSC::CodeSpecializationKind, JSC::JSValue, JSC::LLIntCallLinkInfo*)
20  0x2e2579 llint_slow_path_call
21  0x2ea1ed llint_entry
22  0x2ea1f9 llint_entry
23  0x2ea1f9 llint_entry
24  0x2ea4c1 llint_entry
25  0x2ea1f9 llint_entry
26  0x2e5021 vmEntryToJavaScript
27  0x2a4cd9 JSC::JITCode::execute(JSC::VM*, JSC::ProtoCallFrame*)
28  0x28d713 JSC::Interpreter::executeCall(JSC::ExecState*, JSC::JSObject*, JSC::CallType, JSC::CallData const&amp;, JSC::JSValue, JSC::ArgList const&amp;)
29  0x38be87 JSC::call(JSC::ExecState*, JSC::JSValue, JSC::CallType, JSC::CallData const&amp;, JSC::JSValue, JSC::ArgList const&amp;, WTF::NakedPtr&lt;JSC::Exception&gt;&amp;)
30  0x9e943 NativeScript::GlobalObject::moduleLoaderEvaluate(JSC::JSGlobalObject*, JSC::ExecState*, JSC::JSValue, JSC::JSValue)
31  0x44c4f9 JSC::ModuleLoaderObject::evaluate(JSC::ExecState*, JSC::JSValue, JSC::JSValue)
JavaScript stack trace:
1   onConnected@file:///app/Pages/Home/home.component.js:157:55
2   peripheralDidDiscoverCharacteristicsForServiceError@file:///app/tns_modules/nativescript-bluetooth/bluetooth.js:111:23
3   UIApplicationMain@[native code]
4   start@file:///app/tns_modules/application/application.js:233:26
5   @file:///app/tns_modules/nativescript-angular/application.js:65:26
6   ZoneAwarePromise@file:///app/tns_modules/zone.js/dist/zone-node.js:542:38
7   nativeScriptBootstrap@file:///app/tns_modules/nativescript-angular/application.js:64:23
8   anonymous@file:///app/main.js:5:36
9   evaluate@[native code]
10  moduleEvaluation@[native code]
11  @[native code]
12  promiseReactionJob@[native code]
JavaScript error:
</code></pre>

<p>What have I done wrong?</p>

<h1>Update:</h1>

<p>Following Vladimir's answer, I have this:</p>

<pre><code>for (let i = 0; i &lt; peripheral.service.count; i++) {
   if (peripheral.services.objectAtIndex(i).UUID == 'A000') {
      service = peripheral.services.objectAtIndex(i);
      console.log("selected service: ");
   }
}
</code></pre>

<p>However, I still get this output:</p>

<blockquote>
  <p>JavaScript error:
  file:///app/Pages/Home/home.component.js:98:56: JS ERROR TypeError: undefined is not an object (evaluating 'peripheral.service.count')</p>
</blockquote>