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react-rendered-size

Get the rendered size of a React element without needing to render it

Table of contents

What it is

This will render a ReactElement inside a dummy container outside of the window so that the rendered height and width (based on the width passed) can be calculated. This most common use case for this is for virtually rendered elements (such as items in react-virtualized) that have dynamic size due to content but also need to have their size calculated prior to being rendered on-screen.

What it isn't

Magical. This will not give you a DOM when there isn't one, nor will it calculate the height of items that are display: none;. It also doesn't make the DOM magically faster, so use sparingly to avoid performance implications.

Usage

import React, {
  Component
} from 'react';
import getRenderedSize from 'react-rendered-size';

class App extends Component {
  state = {
    size: {
      height: 0,
      width: 0
    }
  };

  componentWillMount() {
    const size = getRenderedSize(
      <div>
        I am a random element that I want to get the size of for some reason!
      </div>
    );

    this.setState({
      size
    });
  }

  render() {
    const {
      size
    } = this.state;

    return (
      <div>
        The react element in componentWillMount is {size.height} pixels tall and {size.width} pixels wide.
      </div>
    );
  }
}

API

All methods below are available as named exports, and the default export is getRenderedSize.

getRenderedSize(reactElement[, containerWidth[, containerOptions]])

Function to retrieve the size of the reactElement passed. You can also optionally pass a containerWidth (defaults to the document's width), and pass additional options specific to the container. The containerOptions shape:

{
  /*
    custom container to render inside of. defaults to undefined (will create own element internally).
  */
  container: ?HTMLElement,
  /*
    document to use for element creation / manipulation, which is useful for test environments
    where no DOM exists (easy mocking). defaults to browser document.
  */
  doc: ?Object,
  /*
    the type of container that will house the element when rendered off-screen. defaults to 'div'.
  */
  type: ?string
}

Returns an object which contains the calculated size values for the given reactElement. The shape of the returned object:

{
  height: number,
  width: number
}

getRenderedHeight(reactElement[, containerWidth[, containerOptions]])

Convenience function that will only retreive the height that is returned from getRenderedSize. All parameters are the same as getRenderedSize.

getRenderedWidth(reactElement[, containerWidth[, containerOptions]])

Convenience function that will only retreive the width that is returned from getRenderedSize. All parameters are the same as getRenderedSize.

Browser support

  • Chrome (all versions)
  • Firefox (all versions)
  • Opera 15+
  • Edge (all versions)
  • IE 9+
  • Safari 6+

Development

Standard stuff, clone the repo and npm install dependencies. The npm scripts available:

  • dev => run webpack dev server to run example app (playground!)
  • dist => run webpack to build development dist file with NODE_ENV=development
  • dist:minifed => run webpack to build production dist file with NODE_ENV=production
  • lint => run ESLint against all files in the src folder
  • lint:fix => run ESLint against all files in the src folder, running a fix operation if applicable
  • prepublish => runs compile-for-publish
  • prepublish:compile => run lint, test, transpile, dist
  • test => run test functions with NODE_ENV=test
  • test:coverage => run test but with nyc for coverage checker
  • test:watch => run test, but with persistent watcher
  • transpile => run babel against all files in src to create files in lib