Send selection info to iFrame

code.js

figma.on('selectionchange', () => {
  if (figma.currentPage.selection.length > 1) {
    const selection = figma.currentPage.selection.filter(
      node => node.fills.length > 0 && node.fills[0].type === 'SOLID'
    )
    const fills = selection.map(node => node.fills[0])
    const contrast = calculateContrast(fills[0].color, fills[1].color)
    sendContrastInfo(contrast, fills[0].color, fills[1].color)
  }
}