How do I conditionally add attributes to React components?

Question

Is there a way to only add attributes to a React component if a certain condition is met?

I'm supposed to add required and readOnly attributes to form elements based on an Ajax call after render, but I can't see how to solve this since readOnly="false" is not the same as omitting the attribute completely.

The example below should explain what I want, but it doesn't work.

(Parse Error: Unexpected identifier)

function MyInput({isRequired}) {
  return <input classname="foo" {isRequired ? "required" : ""} />
}

Answer 1

Apparently, for certain attributes, React is intelligent enough to omit the attribute if the value you pass to it is not truthy. For example:

const InputComponent = function() {
    const required = true;
    const disabled = false;

    return (
        <input type="text" disabled={disabled} required={required} />
    );
}

will result in:

<input type="text" required>

Update: if anyone is curious as to how/why this happens, you can find details in ReactDOM's source code, specifically at lines 30 and 167 of the DOMProperty.js file.