alert('Hello, javascript,from js file');

var x = 1;

"Hello,javascript";

if (2 > 1){

var a = 1;

var b = 2;

var c = 3;

}

var age = 15;

if (age >= 18) {

alert('adult');

} else {

alert('teenager');

}

new Array(1, 2, 3);

var arr = [1, 2, 3.14, 'Hello', null, true];

arr[0];

var person = {

name: 'Bob',

age: 20,

tags: ['js', 'web', 'mobile'],

city: 'Beijing',

hasCar: true,

zipcode: null

};

person.name;

person.citysss;

var a; // 申明了变量a，此时a的值为undefined

var $b = 1; // 申明了变量$b，同时给$b赋值，此时$b的值为1

var s_007 = '007'; // s_007是一个字符串

var Answer = true; // Answer是一个布尔值true

var t = null; // t的值是null

var a = 123; // a的值是整数123

a = 'ABC'; // a变为字符串

//int i = 123; // b是整数类型变量，类型用int申明

//b = "ABC"; // 错误：不能把字符串赋给整型变量

var xiaoming = {

name: '小明',

birth: 1990,

school: 'No.1 Middle School',

height: 1.70,

weight: 65,

score: null

};

'name' in xiaoming; // true

'grade' in xiaoming; // false

var age = 20;

if (age >= 18) {

alert('adult');

} else {

console.log('age < 18');

alert('teenager');

}

var age = 3;

if (age >= 18) {

alert('adult');

} else if (age >= 6) {

alert('teenager');

} else {

alert('kid');

}

var x = 0;

var i;

for (i=1; i<=10000; i++) {

x = x + i;

}

alert(x);