js遍历对象和遍历数组

遍历一个对象用for in,
遍历一个数组用.length

var x;var txt="";var person={fname:"Bill",lname:"Gates",age:56};  //对象for (x in person){txt=txt + person[x]+"<br>";}

var x;var txt="";cars=["BMW","Volvo","Saab","Ford"];  //数组for (var x=0;x<cars.length;x++){txt=txt+cars[x]+"<br>";}