var color="blue";function changeColor(){if(color=="blue"){color="read";}else{color="blue";}}changeCo
var color="blue"; function changeColor(){ if(color=="blue") { color="read"; }else{ color="blue"; } } changeColor(); alert("Color is now "+color);
function changeColor没有定义color;所以程序往上级作用域搜索;所以color=="blue";如果一直向上找不到;会报错;