Browser Identifier X has already been declared

Question

I am using ES6 with Babel in my project and I am getting an error when I declare one of my const   use strict    const APP   window APP   window APP        const     window     APP personalCard    function                       the error     Uncaught TypeError  Identifier  APP  has already been declared   and that is the whole file  I don t have that declare anywhere else in that file  But I have declared that var in the top of the other files   What do you think it should be

User · Accepted Answer

But I have declared that var in the top of the other files.

That's the problem. After all, this makes multiple declarations for the same name in the same (global) scope - which will throw an error with const.

Instead, use var, use only one declaration in your main file, or only assign to window.APP exclusively.
Or use ES6 modules right away, and let your module bundler/loader deal with exposing them as expected.

User · Answer

I had a very close issue but in my case  it was Identifier  e  has already been declared    In my case caused because of using try    catch  e    var e         where letter e is generated via minifier  uglifier    So better solution could be use catch ex     ex as an Excemption   Hope somebody who searched with the similar question could find this question helpful

User · Answer

The problem solved when I don t use any declaration like var  let or const

User · Answer

Remember that window is the global namespace  These two lines attempt to declare the same variable   window APP           const APP   window APP   The second definition is not allowed in strict mode  enabled with  use strict  at the top of your file    To fix the problem  simply remove the const APP   declaration  The variable will still be accessible  as it belongs to the global namespace

[javascript] Browser: Identifier X has already been declared

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