JS-JS建立数组的三种方法

隐式建立

var arr=["Audi","BMW","Volvo"];

直接实例化

var arr=new Array("Audi","BMW","Volvo");

建立数组并给数组元素赋值

var arr=new Array();
arr[0]="Audi";
arr[1]="BMW";
arr[2]="Volvo";

注意：

console.log(arr.length); //3
arr[4]='jeep';
console.log(arr.length); //5
console.log(arr[3]); //undefined