SOURCE

var $a = 10;
var a = 3.14;
var string = "I am a string";
var notDefined;
var noSpace = null;
document.write($a + "<br/>");
document.write(a + "<br/>");
document.write(string + "<br/>");
document.write(notDefined + "<br/>");
document.write(noSpace + "<br/>");
document.write("---------------------------------<br/>");
//赋值运算符       

var number1 = 10;
var number2 = 20;
var sum = number1 + number2;
var string1 = "Hi";
var string2 = "Heather";
var string1Number1 = string1 + number1;
var string2Number2 = string2 + number2;
var stringNumber1 = number1 + "";
var stringNumber1Number2 = stringNumber1 + number2;

document.write(sum + "<br/>");
document.write(string1Number1 + "<br/>");
document.write(string2Number2 + "<br/>");
document.write(stringNumber1Number2 + "<br/>");
document.write(string1 + string2 + "<br/>");


document.write("---------------------------------<br/>");
var a = 1;
var b = 2;

document.write(a + "<br/>");
document.write(b + "<br/>");
a += b;
document.write(a + "<br/>");
a -= b;
document.write(a + "<br/>");
a *= b;
document.write(a + "<br/>");

a /= b;
document.write(a + "<br/>");
document.write("---------------------------------<br/>");
//比较运算符
var larger = (1+2) > (2+3);
document.write("(1+2) > (2+3) : " + larger +"<br/>");

var smaller = (1+2) < (2+3);
document.write("(1+2) < (2+3) : " + larger +"<br/>");

var largeEqual = (1+2) >= (2+1);
document.write("(1+2) >= (2+1) : " + largeEqual +"<br/>");

var smallEqual = (1+2) <= (2+3);
document.write("(1+2) <= (2+3) : " + larger +"<br/>");

var equal =((2+2) == 4)
document.write("((2+2) == 4) : "+ equal +"<br/>");

var notEqual =((2+2) != 4)
document.write("((2+2) != 4) : "+ notEqual +"<br/>");

document.write("---------------------------------<br/>");
//逻辑运算符

var intersection = true && (1 > 2);

document.write("true && (1 > 2) : "+intersection+"<br/>");

var union = true || (1 > 2);

document.write("true || (1 > 2) : "+union+"<br/>");

var not = !(1 > 2);
document.write("!(1 > 2) : "+not+"<br/>");
document.write("---------------------------------<br/>");
//条件运算符

var condition = (3>5) ? "你" : "我";
document.write('(3>5) ? "你" : "我":' + condition +"<br/>");
document.write("---------------------------------<br/>");
//字符转数字
var a = Number("2018") + 1000;
document.write(a + "<br/>");
document.write("Number('123')：" + Number("123") + "<br/>");
document.write("Number('3.1415')：" + Number("3.1415") + "<br/>");
document.write("Number('hao123')：" + Number("hao123") + "<br/>");
document.write("Number('100px')：" + Number("100px"));

document.write("parseInt('123')：" + parseInt("123") + "<br/>");
document.write("parseInt('3.1415')：" + parseInt("3.1415") + "<br/>");
document.write("parseInt('hao123')：" + parseInt("hao123") + "<br/>");
document.write("parseInt('100px')：" + parseInt("100px")+ "<br/>");
document.write("parseInt('+123')：" + parseInt("+123") + "<br/>");
document.write("parseInt('-123')：" + parseInt("-123")+ "<br/>");

document.write("parseFloat('123')：" + parseFloat("123") + "<br/>");
document.write("parseFloat('3.1415')：" + parseFloat("3.1415") + "<br/>");
document.write("parseFloat('hao123')：" + parseFloat("hao123") + "<br/>");
document.write("parseFloat('100px')：" + parseFloat("100px") + "<br/>");

document.write("---------------------------------<br/>");
//数字转字符串
var a = 2018 +"";
var b = a + 1000;
document.write(b + "<br/>");
var a = 2018 +"";
var b = a.toString() + 1000;
document.write(b + "<br/>");

document.write("---------------------------------<br/>");
/*转义字符*/
document.write("绿叶，给你\"初恋\"般的感觉~");