console 命令行工具 X clear

console

        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/>");

        var number1=10;
        var number2=20;
        var sum=number1+number2;
        var string1="Hi";
        var string2="Heather";
        var string1Number1=string1+string2;
        var number2String2=number2+string2;
        var stringNumber1=number1+"";
        var stringNumber1Number2=stringNumber1+number2;

        document.write(sum+"<br/>");
        document.write(string1Number1+"<br/>");
        document.write(number2String2+"<br/>");
        document.write(stringNumber1+"<br/>");
        document.write(stringNumber1Number2+"<br/>");

        document.write("...............................<br/>");
        //赋值运算符
        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) :"+smaller+"<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) :"+smallEqual+"<br/>");
        var equal =(1+2) == (2+3);
        document.write("(1+2) == (2+3) :"+equal+"<br/>");
        var notEqual =(1+2) != (2+3);
        document.write("(1+2) != (2+3) :"+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/>");
        //字符串转数字
        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"));
        document.write("parseInt('+123')：" + parseInt("+123") + "<br/>");
        document.write("parseInt('-123')：" + parseInt("-123"));

        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"));

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

<!DOCTYPE html> 
<html>
<head>
    <meta charset="utf-8" />
    <title></title>

</head>
<body>
    <script type="text/javascript">
        document.write("Heather1"+"<br/>");
        function callAlert(){
            alert("Welcome2");
        }
    </script>
    <button onclick="alert('welcome1')">点击1</button> 
    <button onclick="callAlert()">点击2</button>
</body>
</html>