Différence entre JavaScript non défini et nul
undefined: It means a variable declared, but no value has been assigned a value.
//example:
var demo;
alert(demo); //shows undefined
alert(typeof demo); //shows undefined
null: Whereas, null in JavaScript is an assignment value.
You can assign it to a variable.
//Example:
var demo = null;
alert(demo); //shows null
alert(typeof demo); //shows object
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