Cannot read property length of undefined

Question

I am trying to simply check if I have an empty input text box but I get this error when I run this in Chrome      Uncaught TypeError  Cannot read property  length  of undefined    Here is how I go about doing it   I check for DOM readiness and then call the function   function walkmydog           when the user starts entering                                                                                                                                                     if document getElementById  WallSearch   value length    0            alert  nothing             if  document addEventListener        document addEventListener  DOMContentLoaded   walkmydog  false

User · Accepted Answer

The id of the input seems is not WallSearch  Maybe you re confusing  that name and id  They are two different properties  name is used to define the name by which the value is posted  while id is the unique identification of the element inside the DOM   Other possibility is that you have two elements with the same id  The browser will pick any of these  probably the last  maybe the first  and return an element that doesn t support the value property

User · Answer

perhaps  you can first determine if the DOM does really exists   function walkmydog           when the user starts entering     var dom   document getElementById  WallSearch        if dom    null           alert  sorry  WallSearch DOM cannot be found            return false                 if dom value length    0           alert  nothing             if  document addEventListener       document addEventListener  DOMContentLoaded   walkmydog  false

[javascript] Cannot read property length of undefined

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