Hoisting clarification in JavaScript

Question

What I know : If variables are initialized without declaration,then it is automatically initialized.

Hoisting in JavaScript only raises the declaration to the top and not the initialization.

What I tried on Google Chrome Console:

console.log(num);

Result:

Uncaught ReferenceError: num is not defined
    at <anonymous>:1:13

Cause: Since hum isn't declared or initialized

num = 9; console.log(num);

Result: 9

Cause: Due to initialization, it is also declared and num gets its value ie 9

console.log(hum); hum = 8;

Result:

VM519:1 Uncaught ReferenceError: hum is not defined
    at <anonymous>:1:13

What I am not able to understand:

since I have initialized hum to 8,it will also get declared and by hoisting in JS,the declaration of hum is hoisted and I should be getting undifined as result. Why isn't it happening?

See this [`doc`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/var#var_hoisting) — Kunal Mukherjee, Aug 19 '20 at 05:13
where did you initialize hum to 6? - not `undeclared` but `undefined` — Samuel Goldenbaum, Aug 19 '20 at 05:23
Does this answer your question? [Javascript function scoping and hoisting](https://stackoverflow.com/questions/7506844/javascript-function-scoping-and-hoisting) — Samuel Goldenbaum, Aug 19 '20 at 05:25
_declarations_ (`var`) are hoisted. Here there is no declarations. — Pac0, Aug 19 '20 at 05:37
Initialiizing an undeclared variable in sloppy mode does not declare it - it adds it as a property of the gobal object. Include `"use strict";` at the start of code to generate errors for assigning to undeclared variables. — traktor, Aug 19 '20 at 05:41

score 1 · Answer 1 · answered Aug 19 '20 at 05:42

JavaScript variables start with the value of undefined if they are not given a value when they are declared (or initialized) using var, let, or const.

console.log(hum); hum = 8; console.log(typeOf(hum));

this will give you undefined as its intialized but not declared.

console.log(hum); var hum = 8; will be hoisted.

For more info,

https://medium.com/coding-at-dawn/how-to-check-for-undefined-in-javascript-bcedd62c8ad

Hoisting clarification in JavaScript

1 Answers1