title: String interpolation in Typescript with string read from file
body: <p>I have read about <a href="http://basarat.gitbooks.io/typescript/content/docs/template-strings.html" rel="nofollow noreferrer" title="Typescript Deep Dive">template strings</a> in Typescript. I'd like to know if I can use them when I've read a string from a file like this:</p>
  
  <pre><code>let xmlPayloadTemplate = fs.readFileSync('payload.xml', 'utf8');
  </code></pre>
  
  <p>If the <code>xmlPayloadTemplate</code> contains a placeholder like <code>${placeholder}</code>, is there a built-in way to perform the substitution so that I can do something like:</p>
  
  <pre><code>let variableMap = {'placeholder' : 'value' }
  xmlPayloadTemplate.interpolate(variableMap)
  </code></pre>
  
  <p>?</p>
  
  <p>I'm aware of <a href="https://stackoverflow.com/q/24850819/412834">a similar question about string interpolation in Javascript</a> but I'd like to know if there is a better way to do it in Typescript.</p>