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JavaScriptIntermediate#es6#collections
JavaScriptBeginner#fundamentals
Difference between null and undefined?
undefined means a variable was declared but never assigned, or a missing property/return. null is an explicit assignment meaning 'no value'. typeof null is 'object' while typeof undefined is 'undefined'.
Example
let a; // undefined let b = null; // intentional empty a == b; // true a === b; // false