How to declare string constants in JavaScript

Question

I want to declare string constants in JavaScript   Is there is a way to do that

User · Answer

Starting ECMAScript 2015  a k a ES6   you can use const  const constantString    Hello     But not all browsers servers support this yet  In order to support this  use a polyfill library like Babel

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Many browsers  implementations  and Node  have constants  used with const   const SOME VALUE    Your string     This const means that you can t reassign it to any other value   Check the compatibility notes to see if your targeted browsers are supported   Alternatively  you could also modify the first example  using defineProperty   or its friends and make the writable property false  This will mean the variable s contents can not be changed  like a constant

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Are you using JQuery  Do you want to use the constants in multiple javascript files  Then read on   This is my answer for a related JQuery question   There is a handy jQuery method called  getScript   Make sure you use the same relative path that you would if accessing the file from your html jsp etc files  i e  the path is NOT relative to where you place the getScript method  but instead relative to your domain path   For example  for an app at localhost 8080 myDomain         document  ready function         getScript   myDomain myScriptsDir constants js            then  if you have this in a file called constants js   var jsEnum       not really an enum  just an object that serves a similar purpose   FOO    foofoo     BAR    barbar       You can now print out  foofoo  with   jsEnum FOO

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There s no constants in JavaScript  but to declare a literal all you have to do is   var myString    Hello World     I m not sure what you mean by store them in a resource file  that s not a JavaScript concept

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Standard freeze function of built-in Object can be used to freeze an object containing constants   var obj         constant 1    value 1     Object freeze obj   obj constant 1    value 2       Silently does nothing obj constant 2    value 3       Silently does nothing   In strict mode  setting values on immutable object throws TypeError  For more details  see https   developer mozilla org en-US docs Web JavaScript Reference Global Objects Object freeze

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You can use freeze method of Object to create a constant  For example   var configObj   timeOut  36000   Object freeze configObj     In this way you can not alter the configObj

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Just declare variable outside of scope of any js function  Such variables will be global

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Of course  this wasn t an option when the OP submitted the question  but ECMAScript 6 now also allows for constants by way of the  const  keyword   https   developer mozilla org en-US docs Web JavaScript Reference Statements const  You can see ECMAScript 6 adoption here

User · Answer

Well  you can do it like so    function         var localByaka      Object defineProperty window   Byaka             get  function                 return localByaka                     set  function val                localByaka   window Byaka    val                          window Byaka    foo     set constant window Byaka    bar      try resetting it for shits and giggles window Byaka     will allways return foo    If you do this as above in global scope this will be a true constant  because you cannot overwrite the window object    I ve created a library to create constants and immutable objects in javascript  Its still version 0 2 but it does the trick nicely  http   beckafly github io insulatejs

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Use global namespace or global object like Constants   var Constants         And using defineObject write function which will add all properties to that object and assign value to it   function createConstant  prop  value        Object defineProperty Constants   prop          value  value        writable  false

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So many ways to skin this cat  You can do this in a closure  This code will give you a read-only   namespaced way to have constants  Just declare them in the Public area     Namespaced Constants var MyAppName    MyAppName Namespace  function  MyAppName          MyAppName Constants Namespace      function  Constants              Private         function createConstant name  val                Object defineProperty MyAppName Constants  name                    value  val                  writable  false                                      Public         Constants FOO   createConstant  FOO   1           Constants FOO2   createConstant  FOO2   1            MyAppName Constants   Constants         MyAppName Constants     MyAppName Constants            MyAppName     MyAppName           Usage   console log MyAppName Constants FOO           prints 1 MyAppName Constants FOO   2  console log MyAppName Constants FOO           does not change - still prints 1

[javascript] How to declare string constants in JavaScript?

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