SOURCE

const ipt = document.getElementById('ipt')
const img = document.getElementById('img')

const toBase64 = file => {
  return new Promise((resolve, reject) => {
    const reader = new FileReader()
    reader.readAsDataURL(file)
    reader.onload = evt => {
      resolve(evt.target.result)
  	}
  })
}

const getWidthAndHeight = baseCode => {
  return new Promise((resolve, reject) => {
    const img = new Image()
    img.src = baseCode
    img.onload = evt => {
      const { width, height } = img
      resolve({ width, height })
    }
  })
}

ipt.onchange = async evt => {
  const file = evt.target.files[0]
  const baseCode = await toBase64(file)
  const obj = await getWidthAndHeight(baseCode)
  img.src = baseCode
  console.log(obj)
}

<input type="file" id="ipt"/>
<img src="" id="img" />