javascript学习笔记1

var mystring; mystring.substring(1,3) mystring.slice(1,3); mystring.slice(4);

mystring.substring(2,-3); mystring.slice(2,-3);

var sMyString = "Tsinghua University";

document.write(sMyString.indexOf("i")+"<br>"); //从前往后

document.write(sMyString.indexOf("i",3)+"<br>"); //可选参数，从第几个字符开始往后找

document.write(sMyString.lastIndexOf("i")+"<br>"); //从后往前

document.write(sMyString.lastIndexOf("i",3)+"<br>"); //可选参数，从第几个字符开始往前找

document.write(sMyString.lastIndexOf("V")+"<br>"); //大写“V”找不到，返回-1

var fNumber = 895.4;

alert(fNumber.toExponential(1));

alert(fNumber.toExponential(2));

var a=11;

document.write(a.toString(2) + "<br>");

document.write(a.toString(3) + "<br>");

document.write(a.toString(8) + "<br>");

document.write(a.toString(16) + "<br>");//转换成16进制

document.write(parseInt("4567red") + "<br>");

document.write(parseInt("53.5") + "<br>");

document.write(parseInt("0xC") + "<br>"); //直接进制转换

document.write(parseInt("isaacshun") + "<br>");

document.write(parseInt("AF",16) + "<br>");

document.write(parseInt("11",2) + "<br>");

document.write(parseInt("011") + "<br>"); //0开头，默认为八进制

document.write(parseInt("011",8) + "<br>");

document.write(parseInt("011",10) + "<br>"); //指定为十进制

document.write(parseFloat("34535orange") + "<br>");

document.write(parseFloat("0xA") + "<br>"); //不再有默认进制，直接输出第一个字符“0”

document.write(parseFloat("435.34") + "<br>");

document.write(parseFloat("435.34.564") + "<br>");

document.write(parseFloat("isaacshun@gmail.com") + "<br>");

var aMap = ["China","USA","Britain"];

alert(aMap);

alert(aMap.toString() + " " + typeof(aMap.toString()));

var aMap = ["China","USA","Britain"];

document.write(aMap.join() + "<br>"); //无参数，等同于toString()

document.write(aMap.join("") + "<br>"); //不用连接符

document.write(aMap.join("][") + "<br>"); //用“][”来连接

document.write(aMap.join("-isaac-") + "<br>");

var sFruit = "apple,pear,peach,orange";

var aFruit = sFruit.split(",");

alert(aFruit.join("--"));

var aFruit = ["apple","pear","peach","orange"];

alert(aFruit.reverse().toString());

var sMyString = "abcdefg";

alert(sMyString.split("").reverse().join(""));

/* split("")将每一个字符转为一个数组元素

reverse()反序数组的每个元素

join("")再最后将数组无连接符的转为字符串

*/

var aFruit = ["pear","apple","peach","orange"];

aFruit.sort();

alert(aFruit.toString());

var stack = new Array();

stack.push("red");

stack.push("green");

stack.push("blue");

document.write(stack.toString() + "<br>");

var vItem = stack.pop();

document.write(vItem + "<br>");

document.write(stack.toString());

var iNumber = Number(prompt("输入一个5到100之间的数字", ""));

if(isNaN(iNumber)) //判断输入的是否是数字

document.write("请确认你的输入正确");

else if(iNumber > 100 || iNumber < 5) //判断输入的数字范围

document.write("你输入的数字范围不在5和100之间");

else

document.write("你输入的数字是:" + iNumber);

iWeek = parseInt(prompt("输入1到7之间的整数",""));

switch(iWeek){

case 1:

document.write("Monday");

break;

case 2:

document.write("Tuesday");

break;

case 3:

document.write("Wednesday");

break;

case 4:

document.write("Thursday");

break;

case 5:

document.write("Friday");

break;

case 6:

document.write("Saturday");

break;

case 7:

document.write("Sunday");

break;

default:

document.write("Error");

}

var aNumbers = new Array();

var sMessage = "你输入了:/n";

var iTotal = 0;

var vUserInput;

var iArrayIndex = 0;

do{

vUserInput = prompt("输入一个数字，或者'0'退出","0");

aNumbers[iArrayIndex] = vUserInput;

iArrayIndex++;

iTotal += Number(vUserInput);

sMessage += vUserInput + "/n";

}while(vUserInput != 0) //当输入为0（默认值）时退出循环体

sMessage += "总数:" + iTotal;

alert(sMessage);

var aNumbers = new Array();

var sMessage = "你输入了:/n";

var iTotal = 0;

var vUserInput;

var iArrayIndex = 0;

do{

vUserInput = prompt("输入一个数字，或者'0'退出","0");

aNumbers[iArrayIndex] = vUserInput;

iArrayIndex++;

}while(vUserInput != 0) //当输入为0（默认值）时退出循环体

//for循环遍历数组的常用方法：

for(var i=0;i<aNumbers.length;i++){

iTotal += Number(aNumbers[i]);

sMessage += aNumbers[i] + "/n";

}

sMessage += "总数:" + iTotal;

alert(sMessage);

var aNumbers = new Array();

var sMessage = "你输入了:<br>";

var iTotal = 0;

var vUserInput;

var iArrayIndex = 0;

do{

vUserInput = Number(prompt("输入一个数字，或者'0'退出","0"));

if(isNaN(vUserInput)){

document.write("输入错误，请输入数字，'0'退出<br>");

break; //输入错误直接退出整个do循环体

}

aNumbers[iArrayIndex] = vUserInput;

iArrayIndex++;

}while(vUserInput != 0) //当输入为0（默认值）时退出循环体

//for循环遍历数组的常用方法：

for(var i=0;i<aNumbers.length;i++){

iTotal += Number(aNumbers[i]);

sMessage += aNumbers[i] + "<br>";

}

sMessage += "总数:" + iTotal;

document.write(sMessage);

for(var i=1;i<10;i++){ //乘法表一共九行

document.write("<tr>"); //每行是table的一行

for(j=1;j<10;j++) //每行都有9个单元格

if(j<=i) //有内容的单元格

document.write("<td style='border:2px solid #004B8A; background:#FFFFFF;'>"+i+"*"+j+"="+(i*j)+"</td>");

else //没有内容的单元格

document.write("<td style='border:none;'></td>");

document.write("</tr>");

}

function ArgsNum(){

return arguments.length;

}

document.write(ArgsNum("isaac",25) + "<br>");

document.write(ArgsNum() + "<br>");

document.write(ArgsNum(3) + "<br>");

function Combination(m,n){

if(n==0) return 1; //每行第一个数为1

else if(m==n) return 1; //最后一个数为1

//其余都是上一行相邻元素相加而来

else return Combination(m-1,n-1)+Combination(m-1,n);

}

function Pascal(n){ //杨慧三角，n为行数

for(var i=0;i<n;i++){ //一共n行

for(var j=0;j<=i;j++) //每行数字的个数即为行号，例如第一行1个数，第二行2个数

document.write(Combination(i,j)+"  ");

document.write("<br>");

}

}

Pascal(10); //直接传入希望得到的杨辉三角的行数

var myDate1 = new Date(); //运行代码前的时间

for(var i=0;i<3000000;i++);

var myDate2 = new Date(); //运行代码后的时间

alert(myDate2-myDate1);

var oMyDate = new Date();

var iYear = oMyDate.getFullYear();

var iMonth = oMyDate.getMonth() + 1; //月份是从0开始的

var iDate = oMyDate.getDate();

var iDay = oMyDate.getDay();

switch(iDay){

case 0:

iDay = "星期日";

break;

case 1:

iDay = "星期一";

break;

case 2:

iDay = "星期二";

break;

case 3:

iDay = "星期三";

break;

case 4:

iDay = "星期四";

break;

case 5:

iDay = "星期五";

break;

case 6:

iDay = "星期六";

break;

default:

iDay = "error";

}

document.write("今天是" + iYear + "年" + iMonth +"月" + iDate + "日," + iDay);

function disDate(oDate, iDate){

var ms = oDate.getTime(); //换成毫秒数

ms -= iDate*24*60*60*1000; //计算相差的毫秒数

return new Date(ms); //返回新的时间对象

}

var oBeijing = new Date(2008,7,8);

var iNum = 100; //前100天

var oMyDate = disDate(oBeijing, iNum);

document.write(oMyDate.getFullYear()+"年"+(oMyDate.getMonth()+1)+"月"+oMyDate.getDate()+"日" + "距离"+oBeijing.getFullYear()+"年"+(oBeijing.getMonth()+1)+"月"+oBeijing.getDate()+"日为"+iNum+"天");

function selectFrom(iFirstValue, iLastValue){

var iChoices = iLastValue - iFirstValue + 1; //计算项数

return Math.floor(Math.random()*iChoices+iFirstValue);

}

var iNum = selectFrom(2,99); //随机选择数字

var aFruits = ["apple","pear","peach","orange","watermelon","banana"];

//随机选择数组元素

var sFruit = aFruits[selectFrom(0,aFruits.length-1)];

alert(iNum + " " + sFruit);

var sUserAgent = navigator.userAgent;

//检测Opera、KHTML

var isOpera = sUserAgent.indexOf("Opera") > -1;

var isKHTML = sUserAgent.indexOf("KHTML") > -1 || sUserAgent.indexOf("Konqueror") > -1 || sUserAgent.indexOf("AppleWebKit") > -1;

//检测IE、Mozilla

var isIE = sUserAgent.indexOf("compatible") > -1 && sUserAgent.indexOf("MSIE") > -1 && !isOpera;

var isMoz = sUserAgent.indexOf("Gecko") > -1 && !isKHTML;

//检测操作系统

var isWin = (navigator.platform == "Win32") || (navigator.platform == "Windows");

var isMac = (navigator.platform == "Mac68K") || (navigator.platform == "MacPPC") || (navigator.platform == "Macintosh");

var isUnix = (navigator.platform == "X11") && !isWin && !isMac;

if(isOpera) document.write("Opera ");

if(isKHTML) document.write("KHTML ");

if(isIE) document.write("IE ");

if(isMoz) document.write("Mozilla ");

if(isWin) document.write("Windows");

if(isMac) document.write("Mac");

if(isUnix) document.write("Unix");