JavaScriptの学習

var name;
var name = "zhang san";
var name; name = "zhang san";

var name = "zhang san";
var name = 'zhang san';

var cost = 8.32;

var yes = true; 
var no = false;

var array = ['hp','apple','lenovo'];
var apple = array[1];

var stu = {"id":1,"name":"zhang san"};
var name = stu.name;

var a = null;

var id = "测试id"; 
id = 1;

var a = 9;
var b = a++;
//结果 a=10 b=9

var a = 5;
a += 5;
//a = 6

var t1 = ['zhang','li'];

var t2 = new Array();
t2[0] = 'zhang' ;
t2[1] = 'li' ;

var t3 = new Array();
t3.push('zhang');
t3.push('li');

var str = '今天是祖国的67岁生日';
alert(str.substring(3,9));