Returning a boolean value in a JavaScript function

Question

I am doing a client side form validation to check if passwords match  But the validation function always returns undefined   function validatePassword errorMessage       var password   document getElementById  password       var confirm password   document getElementById  password confirm        if password value                Check if confirm password matches       if password value    confirm password value                   return false                  else               If password is empty but confirm password is not       if confirm password value                   return false                  return true      Please note that the validatePassword is called from a member function of the Form object   function Form validation fn          Do other stuff    this submit btn   document getElementById  submit       this validation fn   validation fn     Form prototype submit   funciton        var result     if this validation fn             result   this validation fn               result is always undefined    if result                do other stuff

User · Answer

Don t forget to use var let while declaring any variable See below examples for JS compiler behaviour    function  func    return true     isBool   func    console log typeof  isBool         output - string   let isBool   func    console log typeof  isBool         output - boolean

User · Answer

You could simplify this a lot    Check whether one is not empty Check whether they are equal   This will result in this  which will always return a boolean  Your function also should always return a boolean  but you can see it does a little better if you simplify your code   function validatePassword        var password   document getElementById  password       var confirm password   document getElementById  password confirm        return password value         amp  amp  password value     confirm password value                  not empty       and              equal

User · Answer

You could wrap your return value in the Boolean function  Boolean  return value     That ll ensure all falsey values are false and truthy statements are true

User · Answer

An old thread  sure  but a popular one apparently  It s 2020 now and none of these answers have addressed the issue of unreadable code   pimvdb s answer takes up less lines  but it s also pretty complicated to follow  For easier debugging and better readability  I should suggest refactoring the OP s code to something like this  and adopting an early return pattern  as this is likely the main reason you were unsure of why the were getting undefined  function validatePassword        const password   document getElementById  quot password quot       const confirm password   document getElementById  quot password confirm quot        if  password value length     0          return false           if  password value     confirm password value          return false             return true

[javascript] Returning a boolean value in a JavaScript function

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