Preload and Map images

ImageManager.js

class ImageManager {
  constructor () {
    this.wMap = new Map() // Remplace with weakMap ???
  }

  /**
   * Load it before if it nessessary
   * @param  {String}  url The image to load
   * @return {Promise}
   */
  addImage (url) {
    return this._loadImage(url).then(img => {
      this.wMap.set(url, img)
    })
  }

  /**
   * Return an <img>
   * @param  {String}  url The image to load
   */
  getImage (url) {
    return this.wMap.get(url)
  }

  /**
   * Remove an image saved into the list
   */
  deleteImage (url) {
    this.wMap.delete(url)
  }

  /**
   * Load the image with promise
   * @param  {String}  url The image to load
   * @return {Promise}     <img> or catch
   */
  _loadImage (url) {
    return new Promise((resolve, reject) => {
      let downloadingImage = this.getImage(url)
      if (downloadingImage) {
        resolve(downloadingImage)
      } else {
        downloadingImage = new Image()
        downloadingImage.onload = () => {
          resolve(downloadingImage)
        }
        downloadingImage.onerror = reject
        downloadingImage.crossOrigin = 'Anonymous'
        downloadingImage.src = url
      }
    })
  }
}

const imageManager = new ImageManager()
export default imageManager