How do I dynamically set HTML5 data- attributes using react?

You should not wrap JavaScript expressions in quotes.

<option data-img-src={this.props.imageUrl} value="1">{this.props.title}</option>

Take a look at the JavaScript Expressions docs for more info.

Note - if you want to pass a data attribute to a React Component, you need to handle them a little differently than other props.

2 options

Don't use camel case

<Option data-img-src='value' ... />

And then in the component, because of the dashes, you need to refer to the prop in quotes.

// @flow
class Option extends React.Component {

  props: {
    'data-img-src': string
  }

And when you refer to it later, you don't use the dot syntax

  render () {
    return (
      <option data-img-src={this.props['data-img-src']} >...</option>
    )
  }
}

Or use camel case

<Option dataImgSrc='value' ... />

And then in the component, you need to convert.

// @flow
class Option extends React.Component {

  props: {
    dataImgSrc: string
  }

And when you refer to it later, you don't use the dot syntax

  render () {
    return (
      <option data-img-src={this.props.dataImgSrc} >...</option>
    )
  }
}

Mainly just realize data- attributes and aria- attributes are treated specially. You are allowed to use hyphens in the attribute name in those two cases.