#YOU DONT KNOW JS HOISTING CODE#
#YOU DONT KNOW JS HOISTING SERIES#

let do firstly declare in the top of the scope, and do initialize when encounter the let xxx statements.

var do both declare and initialize, the two cannot be split for var. Only initialized variable can be used in a scope. Like other books in the You Don't Know JS series, Scope and Closures dives into trickier parts of the language that many JavaScript programmers simply avoid. Hoisting includes both declare and initialize. You'll learn how and why they work, and how an understanding of closures can be a powerful part of your development skillset. V vy, hm nay mnh s chia s cun sch hay 'You dont know JS' phin bn dch thut Ting Vit. This concise yet in-depth guide takes you inside scope and closures, two core concepts you need to know to become a more efficient and effective JavaScript programmer. Javascript hin ti ang l mt ngn ng hot v rt ng hc. we see the typical metaphor for JS variable scope management, Hoisting.

#YOU DONT KNOW JS HOISTING SERIES#

However, itвЂ™s important to note that this behavior is not reliable and is subject to change in future versions of JavaScript, so itвЂ™s probably best to avoid declaring functions in blocks.No matter how much experience you have with JavaScript, odds are you don't fully understand the language. The You Dont Know JS (YDKJS) series stands in stark contrast to the typical. youdontknowjs is a very popular javascript book series written by Kyle Simpson.-Figured today letвЂ™s do a one minute quick review Shall weSo here.

#YOU DONT KNOW JS HOISTING CODE#

While this all may sound like nothing more than interesting academic trivia, it highlights the fact that duplicate definitions in the same scope are a really bad idea and will often lead to confusing results.ДЇunction declarations that appear inside of normal blocks typically hoist to the enclosing scope, rather than being conditional as this code implies: We provide up 20x the speed of competitors with a 99. While multiple/duplicate var declarations are effectively ignored, subsequent function declarations do override previous ones. If youre looking for fast and reliable web hosting, A2 Hosting is the company for you.

'ES20xx' or just 'JS' are what you should stick to. Some do, but those terms only serve to perpetuate confusion. Don't use terms like 'JS6' or 'ES8' to refer to the language. declaration, because function declarations are hoisted before normal variables. In other words, the JavaScript/JS that runs in your browser or in Node.js, is an implementation of the ES2019 standard. Notice that var foo was the duplicate (and thus ignored) declaration, even though it came before the function foo(). But a subtle detail (that can show up in code with multiple вЂњduplicateвЂќ declarations) is that functions are hoisted first, and then variables.ДЎ is printed instead of 2! This snippet is interpreted by the Engine as: Both function declarations and variable declarations are hoisted.

You dont know js hoisting