console 命令行工具 X clear

console

//赋值运算符
//加法
var a1=4;
a1 +=4;
document.write(a1+"</br>");
//减法
var a2=5;
a2 -=3;
document.write(a2+"</br>");
//乘法
var a3=1;
a3 *=3;
document.write(a3+"</br>");
//除法
var a4=5;
a4 /=2;
document.write(a4+"</br>");

document.write("<br>----------------------</br>");
//比较运算符
var b1=3;
var b2=4;
document.write((b1<b2)+"</br>");
document.write((b1>b2)+"</br>");
document.write((b1==b2)+"</br>");


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

logicOperation=(b1<b2)&&(b1>b2);
document.write(logicOperation+"</br>");

logicOperation=(b1<b2)||(b1>b2);
document.write(logicOperation+"</br>");

logicOperation!=(b1<b2);
document.write(logicOperation+"</br>");

document.write("<br>----------------------</br>");
//number只能识别纯数字的字符串（包括小数点）
//显示类型转化
        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") + "<br/>");
        document.write("Number('-100px')：" + Number("-100px") + "<br/>");

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

        document.write("<br>----------------------</br>");
        var a5=3214;
        var b=1234+'';
        var c=a5.toString() +"hello";
        document.write(c+ "<br/>");
        document.write(b+ "<br/>");

<!DOCTYPE html> 
<html>
<head>
    <meta charset="utf-8" />
    <title></title>
    <script>
        var $a = 10;//变量整型
        var BEGUG=1;//常量
        var string01='I love JS';//字符串（引号成双出现）
        var none=null;//空值
        var b;//未定值类型
        var num01=10;
        var num02=20;
        var string01="Hello";
        var string02="Fengfeng";
        document.write($a+'</br>');
        document.write(BEGUG+'</br>');
        document.write(string01+'</br>');
        document.write(none+'</br>');
        document.write(b+'</br>');
        document.write(num01+num01+'</br>');//数字+数字
        document.write(num01+string01+'</br>');//数字+字符串
        document.write(string01+string02+'</br>');//字符串相加
    </script>
</head>
<body>
</body>
</html>