Javascript tricks. Why (a, b, c) => 5

Question

.

var a,b,c = function() { return 5; };

Variables a and b are undefined, c is a function, so when we do this (a, b, c) (), do we have 5?

Answer 1

The announcement is the same as:

var a;
var b;
var c = function() { return 5; };

or almost the same as:

var a;
var b;
function c() { return 5; };

Using (a,b,c)has nothing to do with the declaration, it just returns the last operand, so (a,b,c)()it’s exactly the same as c()(so far, evaluating a and b has no side effects).

Answer 2

Because it (a,b,c)matters c.

See the comma statement . It works similarly in C, C ++.

Answer 3

:

var f = function(a,b,c){
    return a, b, {x:a+b, y:a+c}
}

f(1,2,3) {x:3, y:4}, , (a,b,c) c.