A null value indicates that an object value is intended to be absent. There are no values in JavaScript that are null, which means they are empty, unknown, or missing. The undefined datatype is the data type for undefined values, which is a great thing for us. To determine if the output is undefined, you compare the output. The direct comparison comes to mind as one of the first methods. To find out if a variable is undefined in JavaScript, you can use several methods and approaches.Īn undefined variable should not be used when performing an operation if you wish to prevent code-throwing errors. Although both imply an empty state, it differs from null. The JavaScript compiler will always return "undefined" for variables that aren't defined. In this article we will show you the solution of JavaScript check for undefined, to determine if a variable/object is undefined in JavaScript, the keyword undefined is available.
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