title: Sequelize - Custom Operators
body: <p>I'm interested in adding a couple custom operators to our usage of the Sequelize ORM. Specifically I want to add on operators that mimic the <a href="https://docs.djangoproject.com/en/2.1/ref/models/querysets/#startswith" rel="nofollow noreferrer">startswith</a> and <a href="https://docs.djangoproject.com/en/2.1/ref/models/querysets/#endswith" rel="nofollow noreferrer">endswith</a> lookup operators that Django has implemented. Looking through the internals on Sequelize, I can't seem to find the place where it would be to inject this kind of logic. In short, the functionality I'd like to implement is something like:</p>
  
  <pre><code>{
      stringField: {
          [Op.startsWith]: 'bl'
      }
  }
  </code></pre>
  
  <p>to produce the desired sql of</p>
  
  <pre><code>WHERE stringField LIKE 'bl%'
  </code></pre>
  
  <p>I know that in the documentation all the examples show manually appending the <code>%</code> symbol but for my purposes I want to be able to dynamically wrap the value based on the operator being used.</p>