React onClick function fires on render

Instead of calling the function, bind the value to the function:

this.props.removeTaskFunction.bind(this, todo)

MDN ref: https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_objects/Function/bind

Because you are calling that function instead of passing the function to onClick, change that line to this:

<button type="submit" onClick={() => { this.props.removeTaskFunction(todo) }}>Submit</button>

=> called Arrow Function, which was introduced in ES6, and will be supported on React 0.13.3 or upper.