hoisting

来源： https://stackoverflow.com/questions/63765387/what-is-the-order-of-hoisting-function-declarations-vs-var-declarations-in-js

来源： https://stackoverflow.com/questions/63337235/what-are-the-benefits-and-drawbacks-of-variable-hoisting-in-programming-language

问题 console.log(a) //output:ƒ a(){} var a = 1; function a(){}; var a = 10; console.log(a) //output:10 ==================== var a = 1; if(true){ function a(){}; var a = 10; } console.log(a) // this code throws Uncaught SyntaxError: Identifier 'a' has already been declared both above code snippets are same except the if block.why does the latter throws error when its permissible in javascript to delcare same variable twice in the same scope with var as below function a(){}; var a = 10; //no error

问题 JavaScript Hoisting confuses me. Is variable initialization hoisted ? i think it is hoisted because we access variable before we declare and initialize it console.log(a); var a = 4; undefined undefined undefined shows that variable a is declare before code execute this is because of hoisting. if i'm wrong please correct me. 回答1: the way this works is that the variable is accessible in the entire program, see the following: 'a' is undefined because it is not declared in the program, however

问题 JavaScript Hoisting confuses me. Is variable initialization hoisted ? i think it is hoisted because we access variable before we declare and initialize it console.log(a); var a = 4; undefined undefined undefined shows that variable a is declare before code execute this is because of hoisting. if i'm wrong please correct me. 回答1: the way this works is that the variable is accessible in the entire program, see the following: 'a' is undefined because it is not declared in the program, however

问题 I was wondering about hoisting. I know if global function name same with global variable, function overwrite variable's name. Is it right? here is my code. (function() { console.log('console.log#1 ' + globalString); // globalString function })(); var globalString = 'I\'m globalString variable'; (function() { console.log('console.log#2 ' + globalString); // string })(); function globalString() { console.log('I\'m globalString function'); } It's result show me like blow console.log#1 function

问题 I was wondering about hoisting. I know if global function name same with global variable, function overwrite variable's name. Is it right? here is my code. (function() { console.log('console.log#1 ' + globalString); // globalString function })(); var globalString = 'I\'m globalString variable'; (function() { console.log('console.log#2 ' + globalString); // string })(); function globalString() { console.log('I\'m globalString function'); } It's result show me like blow console.log#1 function

问题 I do not fully understand why the following displays "hoisted" towards the end. var x = 'set'; var y = function () { // WHAT YOU DON'T SEE -> var x; // is effectively "hoisted" to this line! if (!x) { // You might expect the variable to be populated at this point...it is not // though, so this block executes var x = 'hoisted'; } alert(x); } //... and this call causes an alert to display "hoisted" y(); Any pointers would be appreciated. 回答1: Quoting MDN Docs on var hoisting, Because variable

问题 This question already has answers here : JavaScript closure inside loops – simple practical example (44 answers) Closed 4 years ago . I'm learning some ES6 features and of course came across the let keyword and its new scope (differs from var ) and I came across an example about the tricky scope of var and its hoisting. but I can't fully understand why I get this result: var events = ['click', 'dblclick', 'keydown', 'keyup']; for (var i = 0; i < events.length; i++) { var event = events[i];

问题 I know that the "execution" in JavaScript happens in 2 phases: 1) The Creation phase when the functions and variables are added in the memory, hoisting,the this is create and outer environment 2) The second phases when the code is executed. The question: The variables and functions insides a parent function are added in the memory when the script start or only when the parent function is invoked ? There is any difference between behavior of parameters of a function and variables declared