js之运算符的注意事项

<script>
//var value = window.prompt("请输入值");
//document.writeln(value);

//||将返回第一个不为false 那个值(对象亦可),或者是最后一个值（如果全部都是false的话）比如:
//var a = 4;
//var b = 90;
//var c = a || b;
//window.alert(c);

var a = false;
var b = false;
var d = 0;
var c = b || a || d;
window.alert(c);//输出0

var a = false;
var b = false;
var d = 0;
var obj = new Object();
var c = b || a || d||obj;
window.alert(c);//输出0
</script>