The difference between if (variable) and if (variable ==true) in JavaScript

if (judgment expression) {
Execute content
}

If the expression is true, the contents of the parentheses are executed.
Here, if the variable is not 0,null,undefined,false, it will be handled as true. As long as the variable has a value other than 0 or an object, an array, a string, it will be considered true
Variable ==true, the variable is a bool value, and is true before it is considered compliant.

var a;//defines a variable that is not initialized

if (a) {alert (1) return};//is not executed here, because a has no value, so is false;

a=0//here assigns a value of 0

if (a) {alert (1) return};//is executing this sentence because a=0;0 stands for false, so it is still not executed;

A=1 or a= "123";

if (a) {alert (1) return};//here a= the number except 0, or the character or obj is represented as true, the alert will execute!

var b;

if (b== "") and if (B==null) here who will execute it, of course, is the latter, because B is not defined value, if it is Var b= "", then the first one will be executed;

b = 1;

if (b==1) and if (b== "1") which one will be executed here, the answer is both will execute! Because JS = = = value is equal;

var C;

c=0;

if (C==false) will not execute it, the answer is yes;

C=1;

if (c==true) will do the same! But do we see the following?

c=2 or c= "admin"

if (c==true) alert (1) This sentence will be executed, the answer is no, because the default is that 0 is false and 1 is true, for the other is not so defined, so here will not execute, of course, if you are such if (c) then this will be executed!

The difference between if (variable) and if (variable ==true) in JavaScript