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Posted By

nerdfiles on 03/05/10


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javascript js global vars


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SafelyDeclare

 / Published in: JavaScript
 

To safely declare variables. Well, actually use this to tell before the fact whether you would clobber a var with a name. It won't be declared, and you'll receive a nice, breathy error.

It's more of a diagnostic tool, I suppose.

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  1. function safelyDeclare(varName, varVal) {
  2.     varName = (varName.indexOf("window.") != -1) 
  3.             ? varName = varName.replace("window.", "")
  4.             : varName;
  5.  
  6.     if ( window[varName] || window.varName ) {
  7.         throw new Error("Variable '"+varName+"' is an existing global variable. You may find clobbering it to be an undesirable outcome!");
  8.     } else {
  9.         eval(varName+' = '+varVal+';');
  10.     }
  11. }
  12.  
  13. window.onload = 3;
  14.  
  15. safelyDeclare('window.onload', function() { console.log("My backpack's got jets."); }); // error
  16.  
  17. window.onload();
  18.  
  19.  
  20. boba = 3;
  21.  
  22. safelyDeclare('boba_fett', function() { console.log("My backpack's got jets."); }); //no error since "boba_fett" is not in the [window] object
  23.  
  24. boba_fett();

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