知识点：

1.运算符的优先级训练。

<script type="text/javascript">


var a = 2;
a / = 4;简写形式
a = a/4

a - = 4;简写形式

a = a - 4

 

var t = 1, b = 2 ,c = 4 ,d = 8;
var rs = c*(t/=d)*t + b;
4*1/8*1/8+2 =2.0625

var t = 1, b = 2 ,c = 4 ,d = 8;
var rs = -c*(t/=d)*(t-2) + b;
-4*1/8*(1/8-2)+2

var t = 1, b = 2 ,c = 4 ,d = 8;
var rs = -c/2*((--t)*(t-2)-1) + b;--t 原来的数字减一

var rs = -c/2*(t--*(t-2)-1) + b;         ♥         t-- 返回原来的值，内存的t变为0！！-2*（1*（0-2）-1）+2=8
-2*(0*-1-1)+2=4

 

var t = 1, b = 2 ,c = 4 ,d = 8;
var rs = c/2*(t-=2*t*t+2) + b;
4/2*(t = t - (2*t*t+2))+2
2*(t=1-4)+2
2*-3+2
=-4

var a = 3,b = 5;
b-a!=a&&!b
(( b - a) != a )&&(!b)

((5-3)!= a)&&(!5)
(true)&&(false)

三目运算：

var c = 5>7?"false":"true";

 

var a = "null", b = false;
c = a == b ?"相等":"不相等";
document.writeln(c);

var a = "", b = 0;
c = a == b ?"相等":"不相等";
document.writeln(c);

 

var a = 3,b = 5;
var c = a>b-a&&!b-a||a ?"true":"false"
( ((a > (b - a)) && ((!b) -a)) || a )?"true":"false"
( ((3 > (5 - 3)) && ((!5) -3)) || 3 )?"true":"false"
((ture)&& ((false)-3))||3?"true":"false"
((ture)&& ((0)-3))||3?"true":"false"
((ture)&& (-3)||3?"true":"false"
(-3)||3?"true":"false"
-3?"true":"false"

"true"

</script>