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String object. Number object. Math Object
String Object
The properties and methods of a string object are used to manipulate strings.
<!DOCTYPE html>
<
html
lang
=
"en"
>
<
head
>
<
meta
charset
=
"UTF-8"
>
<
title
>Title</
title
>
</
head
>
<
body
>
<
script
>
var str="I like javascript ";
document.write(str);
document.write(‘<
br
>‘);
// 属性长度
document.write(str.length);
document.write(‘<
br
>‘);
// 转大写
document.write(str.toUpperCase());
document.write(‘<
br
>‘);
// 转小写
document.write(str.toLowerCase());
document.write(‘<
br
>‘);
// 返回指定位置的字符，不包括空
document.write(str.charAt(5));
document.write(‘<
br
>‘);
// 返回字符的位置
document.write(str.indexOf(‘a‘));
document.write(‘<
br
>‘);
// 返回字符最后一次出现的位置
document.write(str.lastIndexOf(‘a‘));
document.write(‘<
br
>‘);
// 从字符串中取指定范围的字符，从开始，包括空格
document.write(str.substring(0,4));
document.write(‘<
br
>‘);
// 将字符串按分解规则分解成数组
var value=str.split(" ");
document.write(value[0]);
document.write(‘<
br
>‘);
// 去年字符串开始和结尾的空格
document.write(str.trim());
document.write(‘<
br
>‘);
// 查看和替换
document.write(str.replace(‘javascript‘,‘C++‘));
document.write(‘<
br
>‘);
</
script
>
</
body
>
</
html
>Math Object
The number object is typically used to manipulate numbers.
<!DOCTYPE html>
<
html
lang
=
"en"
>
<
head
>
<
meta
charset
=
"UTF-8"
>
<
title
>Title</
title
>
</
head
>
<
body
>
<
div
id
=
"info"
></
div
>
<
script
>
var numberOne=12.545678;
// 四舍五入
document.write(numberOne.toFixed());
document.write(‘<
br
>‘);
// 指定有效数个数，这里指定为3
document.write(numberOne.toPrecision(3));
document.write(‘<
br
>‘);
//以指数表示法返回该数值字符串表示形式,可以带参数指定小数位数
document.write(numberOne.toExponential(3));
document.write(‘<
br
>‘);
</
script
>
</
body
>
</
html
>Math ObjectThe math object is used for mathematical calculations, such as calculating squares, rounding, generating random numbers, and so on.
<!DOCTYPE html>
<
html
lang
=
"en"
>
<
head
>
<
meta
charset
=
"UTF-8"
>
<
title
>Title</
title
>
</
head
>
<
body
>
<
script
>
var numberTwo=23.344;
// 常量PI
document.write(Math.PI);
document.write(‘<
br
>‘);
// 生成随机数,0~1,范围从0到1以内,不包括1
document.write(Math.random());
document.write(‘<
br
>‘);
// 将整数，取最近并大于它当前值的数
document.write(Math.ceil(numberTwo));
document.write(‘<
br
>‘);
// 将整数，取最近并小于它当前值的数
document.write(Math.floor(numberTwo));
document.write(‘<
br
>‘);
// 四舍五入
document.write(Math.round(numberTwo));
document.write(‘<
br
>‘);
</
script
>
</
body
>
</
html
>
Javascript&jquery.string object. Number object. Math Object
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