code.ts

if(figma.command == 'removebgfunc') {

  async function checkFill(fill, apiKey) {
    if(fill.type === 'IMAGE') {

      const image = figma.getImageByHash(fill.imageHash)
      const bytes = await image.getBytesAsync()

      figma.showUI(__html__, { visible: false })
      figma.ui.postMessage({
        type: 'run',
        bytes: bytes,
        apikey: apiKey
      })

      const array: Uint8Array = await new Promise((resolve, reject) => {
        figma.ui.onmessage = response => {
          if(typeof response.errors !== 'undefined') {
            figma.closePlugin(response.errors[0].title)
          } else {
            resolve(response as Uint8Array)
          }
        }
      })

      const newImageFill = JSON.parse(JSON.stringify(fill))
      newImageFill.imageHash = figma.createImage(array).hash
      return {
        fill: newImageFill,
        updated: true
      }

    }
    return {
      fill: fill,
      updated: false
    }
  }

  async function removeBG(node, apiKey) {
    let types = ['RECTANGLE', 'ELLIPSE', 'POLYGON', 'STAR', 'VECTOR', 'TEXT']
    if(types.indexOf(node.type) > -1) {
      let newFills = [],
        updated = false,
        check
      for(const fill of node.fills) {
        check = await checkFill(fill, apiKey)
        updated = check.updated || updated
        newFills.push(check.fill)
      }
      node.fills = newFills
      figma.closePlugin(updated ? 'Image background removed.' : 'Nothing changed.')
    } else {
      figma.closePlugin('Select a node with image fill.')
    }
  }

  if(figma.currentPage.selection.length !== 1) {
    figma.closePlugin('Select a single node.')
  }

  figma.clientStorage.getAsync('removeBgApiKey').then(apiKey => {
    if(apiKey) {
      removeBG(figma.currentPage.selection[0], apiKey)
    } else {
      figma.closePlugin('Set API Key first.')
    }
  })

} else if(figma.command == 'removebgkey') {

  figma.clientStorage.getAsync('removeBgApiKey').then(apiKey => {
    figma.showUI(__html__, { visible: true })
    figma.ui.postMessage({
      type: 'key',
      apikey: apiKey
    })
    figma.ui.onmessage = response => {
      figma.clientStorage.setAsync('removeBgApiKey', response).then(() => {
        figma.closePlugin('API Key set.')
      })
    }
  })

}