The Daily WTF

Validating user input is one of those problems that’s deceptively simple. The actual validation rules tend to be simple to describe: this field should be at least ten characters long, that field should match this regex, this one should be a number. But applying those rules can get cumbersome, especially when you write it yourself.

It can quickly get as thorny and difficult as date handling.

Well, Carole inherited some home-brew validation code. It’s been running in the front-end of a web app for years.

const validateGeneral = async function (importantDataStructure) { log.info(`Validating schema for ${importantDataStructure.name} `) let errors = [] try { importantDataStructure.importantField === ‘onlyThisStringIsAllowed’ ? null : errors.push(‘ Invalid importantField’) validations.NAME_VALIDATION.test(importantDataStructure.name) ? null : errors.push(‘ importantDataStructure name has invalid characters’) importantDataStructure.requiredField === undefined ? errors.push(‘ importantDataStructure is missing requiredField’) : null if (errors.length > 0) { log.error(`Errors detected for ${importantDataStructure.name} `) throw new Error(errors.toString().trim()) } } catch (err)

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