Cannot use new with expression typescript : <pre><code>interface Window {
    AudioContext: AudioContext;
    webkitAudioContext: Function
}

let contextClass = window.AudioContext || window.webkitAudioContext;
let context: AudioContext = new contextClass();
</code></pre>

<p>The last line is giving me this error,</p>

<blockquote>
  <p>Cannot use 'new' with an expression whose type lacks a call or
  construct signature</p>
</blockquote>

<p>How can I resolve this?</p>
