Detect if page is loaded inside WKWebView in JavaScript

Question

How can I reliably detect using javascript that a page is loaded inside a WKWebView? I\'d like to be able to detect these scenarios:

• iOS & WKWebView
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Answer 1

Given the change in behavior to the UIWebView that was introduced by Apple in iOS 10, here's a new answer that combines the original response by @Justin-Michael and the follow-up favorite by @hexalys.

var isWKWebView = false ;
if( navigator.platform.substr(0,2) === 'iP' ) {    // iOS detected
    if( window.webkit && window.webkit.messageHandlers ) {
        isWKWebView = true ;
    }
}

It turns out that Justin's answer was really the better feature detection mechanism, because it works for both iOS 9 and iOS 10.

No telling what happens when we get to iOS 11. :-)

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Qualification: this test will work if you are using the official Cordova WKWebView plugin to build your webview app, because that plugin does initialize the addScriptMessageHandler method, as noted by @hexalys in the comments to this post. That mechanism is being used by Cordova to define a new JS to native bridge when the WKWebView plugin is present.

Search for addScriptMessageHandler in that plugin repo and see the very end of the ios-wkwebview-exec.js file in that repo for some implementation details (or search for the string window.webkit.messageHandlers in that file).