数组并接成字符串

join()方法

以指定字符做连接字符，依次连接数组中的项并返回构成的字符串，在不传入参数或者传入参数为undefined时以","拼接。

var colorArr = ["red","green","blue"];

alert(colorArr.join()); //red,green,blue

alert(colorArr.join(undefined)); //red,green,blue

alert(colorArr.join("*")); //red*green*blue