练习

var a = 10 && 20;
console.log(a);
var num = 20 || 30;
console.log(num);
var t = 0 || 20;
console.log(t);
var s = 0 && 30;
console.log(s);
 var a  = "21"+4-true+"3"
var b  = 0 ||"abc";
var c = "abc" || 1;
var d = 0 || NaN;
var a = 10;
a++;   
b = ++a + 2;  
c = ++b + a++ + 4;
console.log(a);
console.log(b);
console.log(c);
 var b = "12"-Boolean("")+true +1;
console.log(b);
var c = "10"+1-Boolean("good")+"";
console.log(c);
var d = "1"+true-false;
console.log(d);
var f =10-""+Boolean("good")-Boolean("word");
console.log(f);