JavaScript的数组定义和长度获取

1、定义

var arr = [元素，元素，元素。。。];

var arr = new Array(元素，元素，元素。。。);

var arr = new Array(3);

arr[0] = 元素;

arr[1] = 元素;

<script type="text/javascript">
    //声明
    //如果一个数组的下标是自定义的，那么该元素就是对象元素（非数组）
    //数组在JavaScript里是对象的一部分
    var color = ["red", "blue", "green"];
    console.log(color);
    console.log(color[1]);

    var animal = new Array("tiger", "wolf", "dog");
    console.log(animal[2]);

    var food = new Array(3);
    food[0] = "bread";
    food[1] = "drink";
    food[2] = "mile";
    food["yuan"] = "元宵";
    console.log(food);
    //对象访问成员：对象[成员名] 或 对象.成员名
    //数组访问元素：数组[下标]
    console.log(food.yuan);
    console.log(food["yuan"]);
</script>

结果：

2、数组长度获取

数组.length

<script type="text/javascript">
    //length给或得数组元素，最大数字下标加1的信息
    //要想获得正确数数组元素，该数组下标必须是0/1/2....
    var color = ["red", "blue", "green"];
    color[3] = "gold";
    color["juse"] = "orange";
    color[10] = "brown";
    console.log(color.length);
</script>