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How to handle a not defined value in JavaScript?
if (oldins == ins)
oldins is not defined.
How do I check this?
312
To solve this error:Load the jQuery library at the beginning of all your javascript files/scripts which uses $ or jQuery, so that $ can be identified in scripts .
If you want to check if a variable exists, that can only be done with try / catch , since typeof will treat an undeclared variable and a variable declared with the value of undefined as equivalent.
This JavaScript exception variable is not defined occurs if there is a non-existent variable that is referenced somewhere. Cause of Error: There is a non-existent variable that is referenced somewhere in the script. That variable has to be declared, or make sure the variable is available in the current script or scope.
A variable that has not been assigned a value is of type undefined . A method or statement also returns undefined if the variable that is being evaluated does not have an assigned value. A function returns undefined if a value was not returned .
if ((typeof(oldins) !== "undefined") && (oldins === ins))
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