hoisting

Are variables declared with let or const not hoisted in ES6?

由 三世轮回 提交于 2019-12-13 02:28:52
问题 I have been playing with ES6 for a while and I noticed that while variables declared with var are hoisted as expected... console.log(typeof name); // undefined var name = "John"; ...variables declared with let or const seem to have some problems with hoisting: console.log(typeof name); // ReferenceError let name = "John"; and console.log(typeof name); // ReferenceError const name = "John"; Does this mean that variables declared with let or const are not hoisted? What is really going on here?

firebug console not doing hoisting

由 ぐ巨炮叔叔 提交于 2019-12-12 14:41:49
问题 console.log(a()); function a(){ console.log("hello"); } From above code, i will expect "hello" (and some undefined s) to be logged on console. But firebug gives ReferenceError: a is not defined So firebug does not do hoisting? 回答1: The reason for the issue is that functions do not hoist when declared inside a child block. by MDN (Much covered here is not standard ECMAScript). Compare the following snippets: alert(c()); function c(){return 42;} and { alert(c()); function c(){return 42;} } The

Javascript - Precedence in hoisting

由 随声附和 提交于 2019-12-12 14:13:58
问题 In hoisting, do variables take precedence over function definition or the other way round? Please see the code below: function a() { var x = 10; function x() { return 20; } return x; } 回答1: It's not a matter of one taking precedence over the other (there is precedence taking place, but that's largely just a matter of semantics). What matters here is that the assignment part of the variable declaration is not hoisted, whereas the entire function definition is . Note Based on raina77ow's answer

JavaScript hoisting for multiple declarations of the same variable

由 点点圈 提交于 2019-12-11 10:49:53
问题 I was trying to understand JavaScript hoisting and from what I have understood, memory space is set aside for all the variable declarations before the execution of the code. I would like to understand how the interpreter works through hoisting in case of multiple declarations for the same variable. Consider the following code: console.log(a); //first declaration function a() { console.log('hello'); } //second declaration var a = 2; The output is the function declaration: function a() {

Define a record type in PL/SQL block that references a collection of itself

由 荒凉一梦 提交于 2019-12-10 23:27:13
问题 How to define a record type in PL/SQL anonymous block that contains a property that is a collection of itself? Look at the following example: DECLARE type t_item is record ( name varchar2(64), children t_items -- referencing t_items type ); type t_items is table of t_item; -- referencing t_item type BEGIN -- script code END PL/SQL has no type hoisting so Oracle engine raises an exception: PLS-00498: illegal use of a type before its declaration How to define a record t_item that contains a

javascript hoisting for global variable

由 ☆樱花仙子☆ 提交于 2019-12-10 17:14:42
问题 I was wondering how javascript hoisting works for global variable. Let's say I have following code snippet: var a = 5; function print(){ console.warn("a",a,b); var a = 10; b=5; console.warn("a",a); } print(); In this case I am getting error "b is not defined". I wonder why Javascript hoisting is not working for global variable. I tried to look for this but getting results only for variable hoisting. Any thoughts?? 回答1: var statements are hoisted. function declarations are hoisted. Assignments

Variable hoisting - “var” with global variable name in function

由 别等时光非礼了梦想. 提交于 2019-12-09 14:05:29
问题 I was practicing some scenario and find a case: Here is fiddle According to closure bar function should have access to var x so I expected to alert 1 and condition get false due to if(!1) but it alerted undefined and condition get true and second alert is with value 10. var x = 1; function bar() { alert(x); if (!x) { var x = 10; } alert(x); } bar(); So I am confused why it is prompting undefined? According to hoisting in a particular scope you define a variable anywhere it is considered as

If statement and variable hoisting

由 ﹥＞﹥吖頭↗ 提交于 2019-12-07 20:16:24
问题 I am learning about variable hoisting in JavaScript, and found this behavior weird: var x = 0; (function () { //Variable declaration from the if statement is hoisted: //var x; //undefined console.log(x); //undefined if (x === undefined) { var x = 1; //This statement jumps to the top of the function in form of a variable declaration, and makes the condition become true. } }()); Is it correct, that in this case, the statement makes the condition true so it can be executed? 回答1: Hoisting hoists

Function Expression itself cannot assign Name to another Value

由 被刻印的时光 ゝ 提交于 2019-12-07 09:44:17
问题 In the code below: (function (){ function test(){};//"function" var test;//"undefined" var printTest = typeof test; document.write(printTest); })(); printTest will display "function" instead of "undefined", which makes sense since from my understanding, any variable declarations are always "hoisted" to the top of the execution context (which in this case is function execution context) This makes the function declaration "test()" to be the one that appears later in the current execution

How hoisting name resolution order works in JavaScript?

由 给你一囗甜甜゛ 提交于 2019-12-06 10:08:22
I came across a interesting quiz function bar() { return foo; foo = 10; function foo() {} var foo = '11'; } alert(typeof bar()); My interpretation is like this (Which is wrong according to console :) ): var foo; // global variable function bar(){ function foo(){} var foo; // Here variable foo should override foo function return foo; // (according to me foo should be variable with undefined value) What is going on here, How JavaScript resolve naming order ? foo = 10; foo = "11"; } Here is a reference which I am reading this In JavaScript, a name enters a scope in one of four basic ways: 1
订阅 hoisting