title: integer hash in range from string
body: <p>I am writing a function that needs to return a 'random' number from a given string,
  starting from:</p>
  
  <pre><code>function hashNumberBetween(str, start, end){
    ....
    return num;
  }
  
  // same string and same length return same number
  hashNumberBetween('getjnigejgr', 0, 10); // 4
  hashNumberBetween('getjnigejgr', 0, 10); // 4
  
  // but, same string and different length return different number
  hashNumberBetween('getjnigejgr', 0, 32); // 15
  
  hashNumberBetween('jukojmnktgo', 0, 10); // 6
  </code></pre>
  
  <p>what is the right way to achieve the same combination given the same string? I reckon it is some sort of hash function. Any online resource I can look at? Might sound a really easy question but I don't know how to search for it.</p>