title: How to ignore a property update of the state in ReactJs?
body: <p>I know that you can use <a href="https://facebook.github.io/react/docs/component-specs.html#updating-shouldcomponentupdate" rel="noreferrer"><code>shouldComponentUpdate</code></a> to decide if render should be called or not. Citing the docs :</p>
  
  <blockquote>
    <p>By default, <code>shouldComponentUpdate</code> always returns true to prevent
    subtle bugs when state is mutated in place, but if you are careful to
    always treat state as immutable and to read only from props and state
    in render() then you can override <code>shouldComponentUpdate</code> with an
    implementation that compares the old props and state to their
    replacements.</p>
  </blockquote>
  
  <p>But my trouble is a bit different. I calculate a value in <code>componentDidUpdate</code> because a need a first render to be able to do my computation, and i'd like to store this value on the state to be able to use it later on in the <code>render</code> function, but I dont want to trigger a render when I modify it.</p>
  
  <p>How would you do it ? Is this the proper way to go ?
  Should I store this value somewhere else ? Directly on the <code>this</code> ?</p>