scope.md

Scopes Discussion

1. What is the scope of variable GLOBAL_DATA in the example below:

<script>
  let GLOBAL_DATA = { value : 1};
</script>

Pretend in the console, that we type: console.log(GLOBAL_DATA);

2. What is the scope of variable x in the examples below:

let x = 1;
{ 
  let x = 2;
}
console.log(x);
var x = 1;
{ 
  var x = 2;
}
console.log(x);

3. What is the scope of variable x in the examples below:

function outerFn(){
    let x = 1;
    function log(){
      console.log(x);
    };
    function run(fn){
      let x = 100;
      fn();
    }
    run(log);
};
outerFn();

4. What do we call this method of scoping:

let x0 = 0;
function fn1(){
  let x1 = 1;
  fn2();
  function fn2(){
    let x2 = 2;
    fn3();
    function fn3(){
      let x3 = 3;
      console.log(x0 + " " + x1 + " " + x2 + " " + x3);
    };
  };
};
fn1();

5. What is the difference between global scope and other scope types and when do we use the global scope?

6. What is the difference between let and var defining a variable?

7. What is the difference between strict mode and sloppy mode?

1. What is the scope of variable GLOBAL_DATA in the example below:

• Global scope .

Pretend in the console, that we type: console.log(GLOBAL_DATA);

let x = 1; { let x = 2; } console.log(x); var x = 1; { var x = 2; } console.log(x);

x = 1 x = 2

What is the scope of variable x in the examples below:

function outerFn(){ let x = 1; function log(){ console.log(x); }; function run(fn){ let x = 100; fn(); } run(log); }; outerFn();

• Global scope .

What do we call this method of scoping:

let x0 = 0; function fn1(){ let x1 = 1; fn2(); function fn2(){ let x2 = 2; fn3(); function fn3(){ let x3 = 3; console.log(x0 + " " + x1 + " " + x2 + " " + x3); }; }; }; fn1();

• lexical scoping

What is the difference between global scope and other scope types and when do we use the global scope?

global scope can be access from any block or scope , but block scope can be access from it's scope. We use global scope when we want to use a variables from any scope.

What is the difference between strict mode and sloppy mode?

Strict mode is a way of writing JavaScript code that enforces stricter rules for certain behaviors. It eliminates some JavaScript silent errors by changing them to throw errors,
Sloppy mode is the default behavior of JavaScript and is less restrictive than strict mode. It allows certain unsafe actions such as accessing the global object and using undeclared variables.

// Strict mode
"use strict";
function test() {
  "use strict";
  var a = 5;
  a = 10;
  a = 15;  // This will throw an error because "a" is  read-only
}

// Sloppy mode
function test() {
  var a = 5;
  a = 10;
  a = 15;  // This will not throw an error 
}

What is the difference between let and var defining a variable?

The main difference between let and var is that scope of a variable defined with let is limited to the block in which it is declared while variable declared with var has the global scope. So we can say that var is rather a keyword which defines a variable globally regardless of block scope.