WKWebView JavaScript Injection to block zoom.

viewport_injection.swift

// Remember to import WebKit at the top of the file

let source = "var meta = document.createElement('meta');" +
            "meta.name = 'viewport';" +
            "meta.content = 'width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=no';" +
            "var head = document.getElementsByTagName('head')[0];" +
            "head.appendChild(meta);"

let userContentController = WKUserContentController()
userContentController.addUserScript(script)

let configuration = WKWebViewConfiguration()
configuration.userContentController = userContentController

let webview = WKWebView(frame: .zero, configuration: configuration)