currency-validator.js

var currencyValidator = {
  format: function (number) {
    return (Math.trunc(number * 1000000000000) / 1000000000000).toFixed(2)
  },
  parse: function (newString, oldNumber) {
    var CleanParse = function (value) {
      return { value: value }
    }
    var CurrencyWarning = function (warning, value) {
      return { 
        warning: warning,
        value: value,
        attempt: newString 
      }
    }
    var NotAValidDollarAmountWarning = function (value) {
      return new CurrencyWarning(newString + ' is not a valid dollar amount', value)
    }
    var AutomaticConversionWarning = function (value) {
      return new CurrencyWarning(newString + ' was automatically converted to ' + value, value)
    }
  
    var newNumber = Number(newString)
    var indexOfDot = newString.indexOf('.')
    var indexOfE = newString.indexOf('e')
    
    if (isNaN(newNumber)) { 
      if (
        indexOfDot === -1 &&
        indexOfE > 0 &&
        indexOfE === newString.length - 1 &&
        Number(newString.slice(0, indexOfE)) !== 0
      ) {
        return new CleanParse(oldNumber)
      } else {
        return new NotAValidDollarAmountWarning(oldNumber)
      }
    }
    
    var newCurrencyString = currencyValidator.format(newNumber)
    var newCurrencyNumber = Number(newCurrencyString)

    if (newCurrencyNumber === newNumber) {
      if (indexOfE !== -1 && indexOfE === newString.length - 2) {
        return new AutomaticConversionWarning(newNumber)
      } else {
        return new CleanParse(newNumber)
      }
    } else {
      return new NotAValidDollarAmountWarning(
        newNumber > newCurrencyNumber
          ? newCurrencyNumber
          : oldNumber
      )
    }
  }
}

Hi, I've been looking at the vue documentation where they utilise your currency validator here -
https://vuejs.org/v2/guide/migration.html#Filters-Outside-Text-Interpolations-removed

I noticed a weird bug when playing about with the currency inputs in the examples.
For example if I try entering 33.33 It will round down to 33.29, making it impossible to enter that amount.

It also happens trying to enter 33.80, rounds down to 33.79, haven't noticed any others :)

@bcoppingHOF,
Try change line 3 to:
return (Math.trunc(number * 1000) / 1000).toFixed(2)

@shibamo works now for 33.33.

I noticed another bug where I enter 1.11 and afterwards add more 1s to the beginning until it will parse to 1111.1
The solution of @shibamo solves it for small numbers, but it will appear again for large numbers.

Thanks for the snippets though :)

In the interest of shameless self-promotion, I deal with some of those bugs at https://github.com/adamcarheden/html-form-tools. vue-compatible version coming soon (maybe).

is perfect and practical code, start it ~
i think adding annotation is a great idea! thanks ~