小结练习

"1"-9+"true"-parseInt(12.34)   // NaN
"9"-8+"false"   // 1false
"9"-8-"false"   // NaN
10+"2"-true-"false" // NaN
"10"+1-true  //100
"10"+1+true  //101true
"10"-1+true  // 10
"10"+true-1  // NaN
"true1"-1    // NaN

var a = 10
var m =a++ + ++a +20  // 10+12+20
console.log(m) // 42
var b = 4
var c = --b +10;  //13

var b = 0 || "abc"   //abc
var c = "abc" || 1;  //abc
var d = 0 || NaN     //NaN
var f = NaN || 0     //0
var a = "abc" && 10   //10
var b = 0 && "abc"    //0

console.log(false == ""); // true
console.log(true == 1); // true
console.log(null == undefined);  // true
console.log(undefined == false);  // false
console.log(1 == "1"); // true
console.log(null == false); // false

      //NaN和任何值做计算，结果一定是NaN
        console.log(Number(undefined));//NaN
        console.log(Number(NaN));//NaN
      console.log(Number(null));//0
      console.log(Number(""));//0
      console.log(Number(false));//0