Understanding Javascript The Weird Part Parts 【2025-2026】

function getObj() return // ASI adds semicolon here → returns undefined ok: true ;

| Binding Rule | Example | this value | |-------------------|----------------------------------|----------------------------| | Default | fn() | window (strict: undefined ) | | Implicit (object) | obj.fn() | obj | | Explicit | fn.call(obj) , fn.apply(obj) | obj | | new binding | new Fn() | new instance | understanding javascript the weird part parts

typeof null; // 'object' (bug in JS) typeof function(){}; // 'function' (but not a separate type) [] instanceof Array; // true [] instanceof Object; // true (arrays are objects) false , 0 , '' (empty string), null , undefined , NaN , -0 , 0n function getObj() return // ASI adds semicolon here

const obj = name: 'Alice', greet() console.log(this.name); ; const greetFn = obj.greet; greetFn(); // undefined (default binding, not implicit) Fix: use arrow functions (lexical this ) or .bind() . The weird part: A function “remembers” its lexical scope even when executed outside it. Dog.prototype.bark = function() return 'woof'

getObj(); // undefined Place { on same line as return . 10. NaN – Not a Number Weird part: NaN is a number type, and it’s not equal to itself.

function Dog(name) this.name = name; Dog.prototype.bark = function() return 'woof'; ; const d = new Dog('Rex'); d.bark(); // 'woof' Weird parts: