What are javascript built-in functions?

In JavaScript, built-in functions refer to functions that come with the browser kernel and can be used directly without introducing any function library. Common built-in functions can be divided into five categories: 1. Regular functions; 2. Array functions; 3. Date functions; 4. Mathematical functions; 5. String functions.

The operating environment of this tutorial: windows7 system, javascript version 1.8.5, Dell G3 computer.

Built-in functions in javascript

js built-in functions come with the browser kernel and can be used directly without introducing any function library function.

Common built-in functions can be divided into five categories:

1, regular function

2, array function

3, Date function

4, math function

5, string function

The first category: regular function

includes the following 9 Functions:

(1) alert function: displays a warning dialog box, including an OK button.

(2)confirm function: Display a confirmation dialog box, including OK and Cancel buttons.

(3)escape function: Convert characters into Unicode codes.

(4)eval function: calculates the result of an expression.

(5)isNaN function: Test whether (true) or not (false) is not a number.

(6)parseFloat function: Convert a string into dotted digital form.

(7)parseInt function: Convert the string into integer digital form (the decimal system can be specified).

(8)prompt function: Display an input dialog box, prompting to wait for user input.

Second Category: Array Function

Includes the following 4 functions:

(1)Join function: Convert and join all elements in the array is a string.

(2)langth function: Returns the length of the array.

(3)reverse function: Reverse the order of array elements.

(4)sort function: Reorder array elements.

The third category: date function

Includes the following 20 functions:

(1)getDate function: returns the "day" part of the date, The value is 1~31

(2)getDay function: returns the day of the week, the value is 0~6, where 0 means Sunday, 1 means Monday,..., 6 means Saturday

(3 )getHours function: Returns the "hour" part of the date, the value is 0~23.

(4)getMinutes function: Returns the "minutes" part of the date, the value is 0~59. See the example above.

(5)getMonth function: Returns the "month" part of the date, the value is 0~11. Among them, 0 represents January, 2 represents March, ..., and 11 represents December. See previous example.

(6)getSeconds function: Returns the "seconds" part of the date, the value is 0~59. See previous example.

(7)getTime function: Returns the system time.

(8)getTimezoneOffset function: Returns the time difference in this region (the regional time difference between local time and GMT Greenwich Mean Time), in minutes.

(9)getYear function: Returns the "year" part of the date. The return value is based on 1900, for example, 1999 is 99.

(10)parse function: Returns the number of milliseconds since 0:00 on January 1, 1970 (local time).

(11)setDate function: Set the "day" part of the date, the value is 0~31.

(12)setHours function: Set the "hour" part of the date, the value is 0~23.

(13)setMinutes function: Set the "minutes" part of the date, the value is 0~59.

(14)setMonth function: Set the "month" part of the date, the value is 0~11. Among them, 0 represents January, ..., and 11 represents December.

(15)setSeconds function: Set the "seconds" part of the date, the value is 0~59.

(16)setTime function: set time. The time value is the number of milliseconds since 00:00 on January 1, 1970.

(17)setYear function: Set the "year" part of the date.

(18)toGMTString function: Convert the date into a string, which is GMT Greenwich Mean Time.

(19)setLocaleString function: Convert date into string and local time.

(20) UTC function: Returns the number of milliseconds since 0:00 on January 1, 1970, calculated in GMT Greenwich Mean Time.

var myDate=new Date(dtime.replace(/-|\./g,"/"));
myDate.getYear();        //获取当前年份(2位)
myDate.getFullYear();    //获取完整的年份(4位,1970-????)
myDate.getMonth();       //获取当前月份(0-11,0代表1月)
myDate.getDate();        //获取当前日(1-31)
myDate.getDay();         //获取当前星期X(0-6,0代表星期天)
myDate.getTime();        //获取当前时间(从1970.1.1开始的毫秒数)
myDate.getHours();       //获取当前小时数(0-23)
myDate.getMinutes();     //获取当前分钟数(0-59)
myDate.getSeconds();     //获取当前秒数(0-59)
myDate.getMilliseconds();    //获取当前毫秒数(0-999)
myDate.toLocaleDateString();     //获取当前日期
var mytime=myDate.toLocaleTimeString();     //获取当前时间
myDate.toLocaleString( );        //获取日期与时间

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Fourth Category: Mathematical Functions

The functions have the following 18:

(1)abs function: Math.abs (the same below) ), returns the absolute value of a number.

(2) acos function: Returns the inverse cosine value of a number, and the result is 0 to π radians (radians).

(3)asin function: Returns the arcsine value of a number, and the result is -π/2~π/2 radians.

(4)atan function: Returns the arctangent value of a number, and the result is -π/2~π/2 radians.

(5)atan2 function: Returns the polar coordinate angle value of a coordinate.

(6)ceil function: Returns the smallest integer value of a number (greater than or equal to).

(7)cos function: Returns the cosine value of a number, and the result is -1~1.

(8)exp function: Returns the power value of e (natural logarithm).

(9)floor function: Returns the maximum integer value of a number (less than or equal to).

(10)log function: natural logarithm function, returns the natural logarithm (e) value of a number.

(11)max function: Returns the maximum value of two numbers.

(12)min function: Returns the minimum value of two numbers.

(13)pow function: Returns the power of a number.

(14)random function: Returns a random value between 0 and 1.

(15)round function: Returns the rounded value of a number, the type is integer.

(16)sin function: Returns the sine value of a number, and the result is -1~1.

(17)sqrt function: Returns the square root value of a number.

(18)tan function: Returns the tangent value of a number.

Fifth Category: String Function

Includes the following 20 functions:

(1)anchor function: generates a link point (anchor) Used as a hyperlink. The anchor function sets the name of the link point of , and the other function link sets the URL address of .

(2)big function: Increase the font size to one, which is the same as the ... tag.

(3)blink function: Makes the string blink, which is the same as the ... tag result.

(4)bold function: Make the font bold, which is the same as the ... tag result.

(5)charAt function: Returns a character specified in the string.

(6)fixed function: Set the font to a fixed-width font, which is the same as the ... tag.

(7)fontcolor function: Set the font color, which is the same as the tag result.

(8)fontsize function: Set the font size, which is the same as the tag result.

(9)indexOf function: Returns the first index found in the string, starting from the left.

(10) italics function: Make the font italic, which is the same as the ... tag result.

(11)lastIndexOf function: Returns the first subscript index found in the string, starting from the right.

(12)length function: Returns the length of the string. (Without parentheses)

(13) link function: Generate a hyperlink, which is equivalent to setting the URL address of .

(14)small function: Reduce the font size by one size, which is the same as the ... tag.

(15)strike function: Add a horizontal line in the middle of the text, which is the same as the ... tag.

(16)sub function: Display the string as a subscript.

(17)substring function: Returns several characters specified in the string.

(18)sup function: Display the string as superscript.

(19)toLowerCase function: Convert the string to lowercase.

(20)toUpperCase function: Convert the string to uppercase.

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