typeof

Author: nilajcoder

JavaScript Interview/Most Imp MCQ/typeof.js

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+let x;
+console.log(typeof x); // "undefined"
+
+let y = 10;
+console.log(typeof y); // "number"
+
+let z = 10.25;
+console.log(typeof z); // "number"
+
+let a = true;
+console.log(typeof a); // "boolean"
+
+let b = "nilaj";
+console.log(typeof b); // "string"
+
+let c = null;
+console.log(typeof c); // "object" ❗ (this is a JS quirk/bug)
+
+let d = BigInt(8);
+console.log(typeof d); // "bigint"
+
+let e = Symbol("hi");
+console.log(typeof e); // "symbol"
+
+
+
+
+console.log(typeof NaN); // "number"  ❗ (NaN means "Not a Number", but still a number type)
+
+console.log(typeof Infinity); // "number"
+
+console.log(typeof []); // "object"  ❗ (Array is technically an object)
+
+console.log(typeof {}); // "object"
+
+console.log(typeof function(){}); // "function"  ✅ (Special case)
+
+console.log(typeof new Date()); // "object"
+
+console.log(typeof null); // "object" ❗ (JS bug)
+
+
+console.log(isNaN(NaN)); // true
+console.log(isNaN("hello")); // true (because "hello" is not a number)
+console.log(isNaN(123)); // false