javascript- Uncaught SyntaxError: Identifier * has already been declared

Question

console.log(a) //output:ƒ a(){}
var a = 1;
function a(){};
var a = 10;
console.log(a) //output:10

====================

var a = 1;
i         


        

Answer 1

Case 1

console.log(a) //output:ƒ a(){}
var a = 1;
function a(){};
var a = 10;
console.log(a) //output:10

Will be rendered as

var a;
a = function(){}; // now a holds the value as a function
console.log(a); // output : f a(){}
a = 1; // a is a var that holds value 1
a = 10; // a is a var that holds value 10
console.log(a); // output : 10

Case 2

var a = 1;
if(true){
   function a(){};
   var a = 10;
}
console.log(a)

Will be rendered as

var a;
a = 1;
if(true) {
    a = function() {};
    let a; // The function declaration in the block uses ES6 declaration semantics (like let or const), which does not allow re-declarations.
    var a; // throws Uncaught SyntaxError: Identifier 'a' has already been declared
    a = 10;
}
console.log(a);

Case 3

var a = 1;
if(true){
    function a(){};
    a = 10;
 }
console.log(a)

Will be rendered as

var a;
a = 1;
if(true) {
    a = function() {};
    let a;
    a = 10;
}
console.log(a); // output : f a(){}

Case 4

var a = 1;
if(true){
    var a= function(){console.log()}
    a = 10;
}
console.log(a)

Will be rendered as

var a;
a = 1;
if(true) {
    a = function(){console.log()}
    a = 10;
}
console.log(a) // output:10

Case 5

var a = 1;
if(true){
    function a(){};
    a = 10;
    console.log(a) 
}
console.log(a) 

Will be rendered as

var a;
a = 1;
if(true){
    a = function() {};
    let a;
    a = 10;
    console.log(a); // output:10
}
console.log(a); // output : f a(){}