React Tutorial: TypeError: Cannot read property 'props' of undefined

Question

I decided to learn React and started with the official tutorial. All is good until I get to this state of my code:

var CommentBox = React.createClass({
  ren         


        

Answer 1

I had the same error message:

Cannot read property 'props' of undefined

...but from a different cause: when this is called from within a function, javascript can not reach the variable because this is in an outer scope. (Note: I was in ES5)

In this case, simply store this in another variable, prior to the function (in the scope of your component): var that = this;

Then you will be able to call that.props from within the function.

Hope this helps for other people who had that error message.

Detailed example below:

render: function() {
  var steps = [];
  var that = this;  // store the reference for later use
  var count = 0;
  this.props.steps.forEach(function(step) {
      steps.push();  // here you are
      count += 1;
  });
  return (
    
{steps}
  )
}