Functions are a type of object which are a type of value. Values can be stored in variables (and properties, and passed as arguments to functions, etc). A function declaration: Creates a named function Creates a variable in the current scope with the same name as the function (unless such a variable already exists) Assigns … Read more
Yes, blocks are going to replace IEFEs, as soon as block-scoped declarations (functions, let/const/class) become widely adopted. You need a scope, e.g. for a closure? Here you have a block, be it a loop body or just part of a statement list. However, there is still one application of IEFEs that blocks cannot replace: the … Read more
You have just stumbled on a js “feature” called hoisting var myname = “global”; // global variable function func() { alert(myname); // “undefined” var myname = “local”; alert(myname); // “local” } func(); In this code when you define func the compiler looks at the function body. It sees that you are declaring a variable called … Read more
In JavaScript variables are moved to the top of script and then run. So when you run it will do var myVar1; alert(myVar1); return false; This is because JavaScript doesn’t really have a true sense of lexical scoping. This is why it’s considered best practice to have all your variables declared at the top of … Read more
Quoting MDN Docs on var hoisting, Because variable declarations (and declarations in general) are processed before any code is executed, declaring a variable anywhere in the code is equivalent to declaring it at the top. This also means that a variable can appear to be used before it’s declared. This behavior is called “hoisting”, as … Read more
After doing some more research, I’ve found: Imports ARE hoisted! according to the spec of ModuleDeclarationInstantiation ALL the dependent Modules will be loaded before running any code. This code will have no errors, and will work: localFunc(); import {myFunc1} from ‘mymodule’; function localFunc() { // localFunc is hoisted myFunc1(); }
Variable hoisting One of the simplest uses of hoisting is variable hoisting. If we didn’t have variable hoisting, this would throw a ReferenceError: var bar = foo; var foo; That doesn’t seem immediately useful, but it allows us to do things like this: var myCoolJS = myCoolJS || {}; This basically means what it looks … Read more
This is surprising as javascript var doesn’t respect block scope but functional scope… Sure, but you didn’t use var for the declaration of a in the block scope. You used a function declaration, which does respect block scopes (otherwise it would be completely invalid code, as in ES5 strict mode). It’s permissible in javascript to … Read more
Function hoisting — the process that evaluates function statements before the rest of the function — is part of the ECMAScript standard IIRC (I can’t find a reference right now, but I recall seeing discussions of EMCAScript that mention it). The evaluation of script tags is part of the HTML standard. It does not specify … Read more
The global a is set to 1 b() is called function a() {} is hoisted and creates a local variable a that masks the global a The local a is set to 10 (overwriting the function a) The global a (still 1) is alerted