javascript questions with console.log

Javascript questions

var a={},
b={key:'b'},
c={key:'c'};
a[b]=123;
a[c]=456;
console.log(a[b]);
console.log(a);

Output:

456
{ '[object Object]': 456 }

============================
(function() {
    console.log(1); 
    setTimeout(function(){console.log(2)}, 1000); 
    setTimeout(function(){console.log(3)}, 0); 
    console.log(4);
})();

Output:

1
4
3
2

============================
(function() {
    console.log(1); 
    setTimeout(function(){console.log(2)}, 1000); 
    setTimeout(function(){console.log(3)}, 0); 
    setImmediate(function(){console.log(5)}); 
    
    console.log(4);
})();

Output:

1
4
3
5
2

==========================================
console.log(0.1 + 0.2);
console.log(0.1 + 0.2 == 0.3);

Output:

0.30000000000000004
false

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

getName();            
console.log(x);
var x = 7;
function getName() {
    console.log('hi');
}

Output:

hi
undefined

=========================================
console.log([] == [])
Output:

false

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