javascript 复习笔记----注意事项总结

v永远不要测试某个特定的浮点数值

if(a+b==0.3){//不要做这样的测试！alert("Yougot0.3.");}

varnum1=25;

varnum2=-num1-1;

alert(num2);//"-26"

alert(sum(10,10));functionsum(num1,num2){

returnnum1+num2;}//声明式正确

alert(sum(10,10));varsum=function(num1,num2){

returnnum1+num2;};//函数表达式，执行错误！！！“unexpectedidentifier”（意外标识符）错误

window.color="red";

varo={color:"blue"};

functionsayColor(){

alert(this.color);

}

sayColor();//red

sayColor.call(this);//red

sayColor.call(window);//red

sayColor.call(o);//blue

functionfactorial(num){

if(num<=1){

return1;

}else{

returnnum*arguments.callee(num-1);//严格模式下，不能通过脚本访问arguments.callee

}

}

varfactorial=(functionf(num){

if(num<=1){

return1;

}else{

returnnum*f(num-1);

}

});

(function(){

//这里是块级作用域

})();