QL code and tests for C#/C++/JavaScript.

javascript/ql/src/React/examples/UnusedOrUndefinedStateProperty.js

@@ -0,0 +1,16 @@
+class Clock extends React.Component {
+    constructor(props) {
+        super(props);
+        this.state = { };
+    }
+
+    render() {
+         // BAD: this.state.date is undefined
+        var now = this.state.date.toLocaleTimeString();
+        return (
+                <div>
+                <h2>The time is {now}.</h2>
+                </div>
+        );
+    }
+}

javascript/ql/src/React/examples/UnusedOrUndefinedStateProperty_fixed.js

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+class Clock extends React.Component {
+    constructor(props) {
+        super(props);
+        this.state = { date: new Date() };
+    }
+
+    render() {
+         // GOOD: this.state.date is defined above
+        var now = this.state.date.toLocaleTimeString()
+        return (
+                <div>
+                <h2>The time is {now}.</h2>
+                </div>
+        );
+    }
+}

javascript/ql/src/React/examples/unsupported-state-update-in-lifecycle-method.js

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+class MyComponent extends React.Component {
+
+    constructor(props) {
+        super(props)
+        this.setState({
+            counter: 0
+        })
+
+    }
+
+    render() {
+        return <div>{this.state.counter}</div>
+    }
+
+}

javascript/ql/src/React/examples/unsupported-state-update-in-lifecycle-method_fixed.js

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+class MyComponent extends React.Component {
+
+    constructor(props) {
+        super(props)
+        this.state.counter = 0;
+    }
+
+    render() {
+        return <div>{this.state.counter}</div>
+    }
+
+}