处理数字

 const digitsRE = /(\d{3})(?=\d)/g\

export function currency (value, currency, decimals) {
value = parseFloat(value)
if (!isFinite(value) || (!value && value !== 0)) return ''
currency = currency != null ? currency : '$'
decimals = decimals != null ? decimals : 2
var stringified = Math.abs(value).toFixed(decimals)
var _int = decimals
  ? stringified.slice(0, -1 - decimals)
  : stringified
var i = _int.length % 3
var head = i > 0
  ? (_int.slice(0, i) + (_int.length > 3 ? ',' : ''))
  : ''
var _float = decimals
  ? stringified.slice(-1 - decimals)
  : ''
var sign = value < 0 ? '-' : ''
return sign + currency + head +
  _int.slice(i).replace(digitsRE, '$1,') +
  _float

}