True and false of values in JavaScript

The values for Flase are:

False0  

All but the above are ture, including "0" (zero in quotes), "false" (false in quotes) , empty functions, [] (empty array), and {} ( Empty objects), are all true

var a =!! (0);    Falsevar B =!! ("0");  True

A comparison between types that are false:

false ,  0 (zero), and "" (empty string) These three are all equal to "= ="

var c = (false = = 0); Truevar D = (false = = ""); True  var e = (0 = = ""); True  

NULL and the undefined is equal to, except for themselves, "= =" compared to other values.

var F = (Null = = False); False  var g = (Null = = NULL);//True  var h = (undefined = = undefined);//Truevar i = (undefined = = null);// True  

There's a special Nan, and he's not equal to any of the values.

var j = (NaN = = null); False  var  k = (Nan = = nan); //False

typeof (NaN) returns the "number", generally we use IsNaN () to determine whether a value is NaN

Above, if the use of "= = =" Strictly congruent and "!==" strict unequal, the situation is not quite the same, the two comparisons are included in the type and value

var L = (false = = 0); Truevar m = (false = = = 0); False

Two applicable methods are attached:

1. Check if an empty array is bit

var n =  ([].length = = 0)  //Ture

2. Check if a bit empty object

var obj = {};for (var i in obj) {    if (Obj[i]) {        return true;    } else {        return false;}    }