getStyles.js

const camelCaseToKebabCase = (value) => {
  if (typeof value !== 'string') return value

  return value.replace(/[A-Z]/g, (char, index, wholeValue) => {
    return wholeValue[index] = `${index === 0 ? '' : '-'}${char.toLowerCase()}`
  })
}

const getStyles = (element) => {
  const elementStyles = {}
  const appliedStyles = getComputedStyle(element)
  const styleKeys = Object.keys(appliedStyles).filter((x) => Number.isNaN(Number(x)))
  styleKeys.forEach((styleKey) => {
    if (appliedStyles[styleKey]) {
      const property = camelCaseToKebabCase(styleKey)
      elementStyles[property] = appliedStyles[styleKey]
    }
  })
  
  return elementStyles
}

/*
In Chrome console you can do:
- copy(getStyles(document.getElementById('your-id-selector')))
- pick an element in Chrome elements -> in console: copy(getStyles($0))
*/

@d7my11 got an error when I tried to test it on Twitter.

@camara90100 because getStyles expects an element, but you can do:

Array.from(document.getElementsByClassName('')).map(getStyles)