求能整出5的数的和及平均值
<html lang="en"> <head> <meta charset="UTF-8"> <title>求能整出5的数的和及平均值</title> </head> <body> <script> var arr = [];/*声明空数组，用来装复合条件的数据*/ for (var i = 1; i < 100; i++) { if (i % 5 == 0) { arr.push(i);/*把符合条件的数据装入数组*/ } } var sum = 0; for (var i = 0; i < arr.length; i++) { /*把数组的所有数据求和，不能<=arr.length*/ sum += arr[i]; } alert(sum); alert(sum / arr.length); </script> </body> </html>
结果图:
传值和引用
<html lang="en"> <head> <meta charset="UTF-8"> <title>传值和传引用</title> </head> <body> </body> <script> /*基本数据类型*/ var zhangHeight = 180; var liHeight = zhangHeight; zhangHeight = 185; alert(liHeight); /*引用数据类型： 传引用*/ var zhangSan = [180,75]; var liSi = zhangSan; zhangSan[0] = 185; zhangSan[1] = 80; alert(liSi[0]); alert(liSi[1]); </script> </html>
结果图:
数字
<html lang="en"> <head> <meta charset="UTF-8"> <title>数字</title> </head> <body> </body> <script> // console.log(Number.MAX_VALUE);/*数字的最大值*/ // console.log(Number.MIN_VALUE);/*数字的最小值*/ // console.log(Number.NEGATIVE_INFINITY);/*负无穷大*/ // console.log(Number.POSITIVE_INFINITY);/*正无穷大*/ // /*NaN：非数字*/ // // var i = 5; // var j; // var result = i + j; // alert(result); // /*not a number NaN*/ var arr = 5; var result = arr.toString();/*把数字转换成字符串*/ alert(typeof(result)); var arr =["zhangsan","lisi"]; var result = arr.toString();/*把数组转成字符串*/ console.log(typeof result); var b = true; var result = b.toString(); console.log(result); </script>
结果图:
字符串
<html lang="en"> <head> <meta charset="UTF-8"> <title>字符串</title> </head> <body> </body> <script> var s = "杰 瑞 教 育"; console.log(s.length);/*把字符串当作是字符数组*/ var a = "abc"; console.log(a.toUpperCase());/*把小写转换成大写*/ var a1 = "JREDU"; console.log(a1.toLowerCase());/*把大写转换成小写*/ var a2 = "jerei"; console.log(a2.charAt(2));/*获取字符串中制定索引处的字符*/ var a3 = "HelloWorld"; /*返回字符串中某个字符串第一次出现的索引位置 参数1：要查找的子元素 参数2：查找的开始位置*/ console.log(a3.indexOf("o",5)); /*subString:与数组的slice方法类似，用于截取字符串的某一段字符 * 参数1：截取的开始索引（包含） * 参数1：截取的结束索引（不包含）*/ var a4 = "this is js"; var result = a4.substring(5,7); console.log(result); </script> </html>
结果图:
日期
<html lang="en"> <head> <meta charset="UTF-8"> <title>日期</title> </head> <body> <div id="time"></div> </body> <script> setInterval(function () { var date = new Date(); var year = date.getFullYear();/*获取年*/ console.log(year); var month = date.getMonth()+1;/*获取月份 +1*/ console.log(month); var day = date.getDate();/*获取日期*/ console.log(day); var hour = date.getHours();/*获取小时*/ console.log(hour); var min = date.getMinutes();/*获取分钟*/ console.log(min); var sec = date.getSeconds();/*获取秒*/ console.log(sec); var mSec = date.getMilliseconds();/*获取毫秒*/ console.log(mSec); var week = date.getDay() == 0?7 :date.getDay();/*获取星期*/ console.log(week); var s =year+"年"+month+"月"+day+"日"+" "+hour+":"+min+":"+sec+" "+"星期"+week; var time = document.getElementById("time").innerHTML = s; },1000); </script> </html>
结果图:
数学类
<html lang="en"> <head> <meta charset="UTF-8"> <title>数学类</title> </head> <body> </body> <script> var pi =Math.PI; console.log(pi); var r = Math.random();/*随机生成一个0 - 1之间的数*/ console.log(Math.floor(r*11));/*floor:向下取整*/ var i = -3.2; console.log(Math.abs(i));/*取绝对值*/ console.log(Math.floor(i));/*floor：向下取整 忽略小数位置*/ console.log(Math.ceil(i));/*ceil:向上取整 小数不为0，整数就+1*/ console.log(Math.round(i));/*round：四舍五入取值*/ var result = Math.max(8,9,22,34);/*比较多个数的最大值*/ var result1 = Math.min(8,9,22,34);/*比较多个数的最小值*/ console.log(result); console.log(result1); var i = 5; var result = Math.pow(i,3); /*pow:求一个数的几次幂*/ console.log(result); </script> </html>
结果图:
Object:对象
<html lang="en"> <head> <meta charset="UTF-8"> <title>Object:对象</title> </head> <body> </body> <script> // var zhangSan = new Object(); // zhangSan.name = "zhangsan"; // zhangSan.age = "25"; // zhangSan.height = "180"; // zhangSan.eat = function () { // alert("我会吃饭！") // }; var zhangSan = { name:"zhangsan", age:"25", height:"160", eat:function () { alert("我会吃饭！") } }; showMessage(zhangSan); function showMessage(person) { console.log(person.name);/*person.name可用peron[name]替换*/ console.log(person.age); console.log(person.height); } </script> </html>
结果图:
