What are the JS functions

JavaScript built-in functions (built-in functions, built-in keywords)
　　
　JS's built-in object is JS, which encapsulates a number of common methods. Common JS built-in objects are: String,date,array,math, etc.
　

JS built-in function is the browser kernel comes with, without any function library introduction can be directly used by the function. JavaScript built-in functions can be divided into five categories:
1. General functions
2. Array functions
3. Date function
4. Mathematical Functions
5. String functions

First Class: General functions
The following 9 functions are included:
(1) Alert function: Displays a warning dialog box, including an OK button. 
(2) Confirm function: Displays a confirmation dialog box, including OK, Cancel button. 
(3) Escape function: Converts a character to a Unicode code. 
(4) eval function: Evaluates the result of an expression. 
(5) isNaN function: The test is (true) No (false) is not a number. 
(6) parsefloat function: Converts a string into a numeric form of a character. 
(7) parseint function: Converts a string into an integer number form (which can be specified as a binary). 
(8) Prompt function: Displays an input dialog box prompting for user input. 

Class II: Array Functions
The following 4 functions are included:
(1) Join function: Converts and joins all elements in an array to a string. 
(2) langth function: Returns the length of the array. 
(3) Reverse function: Reverses the order of the array elements. 
(4) Sort function: Reorder the array elements. 
 
Class III: Date Functions
The following 20 functions are included:
(1) getdate function: Returns the "Day" part of the date with a value of 1~31
(2) getday function: Returns the day of the week with a value of 0~6, where 0 represents Sunday, 1 means Monday, ..., 6 means Saturday
(3) gethours function: Returns the "hour" portion of the date, with a value of 0~23. 
(4) getminutes function: Returns the "minute" part of the date with a value of 0~59. See the example above. 
(5) getmonth function: Returns the month portion of the date, with a value of 0~11. 0 means January, 2 means March, ..., and 11 means December. See the previous example. 
(6) getseconds function: Returns the "second" part of the date with a value of 0~59. See the previous example. 
(7) gettime function: Returns the system time. 
(8) getTimezoneOffset function: Returns the difference in this area (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 a 1900-year base, for example, 1999 is 99. 
Parse Function: Returns the number of milliseconds (local time) that was counted from zero January 1, 1970. 
(one) setdate function: The "day" portion of the set date, with a value of 0~31. 
sethours function: The "hours" section of the set date, with a value of 0~23. 
setminutes function: The "Minutes" section of the set date, with a value of 0~59. 
setmonth function: Sets the month portion of the date, and the value is 0~11. 0 of them represent January, ..., 11 means December. 
() setseconds function: The "Seconds" section of the set date, and the value is 0~59. 
() settime function: Set the time. The time value is the number of milliseconds since January 1, 1970 when the integer count is zero. 
() setyear function: The "Year" section of the set date. 
togmtstring Function: The conversion date becomes a string, GMT Greenwich Standard Time. 
() setlocalestring function: Converts the date into a string, for local time. 
UTC Function: Returns the number of milliseconds from January 1, 1970 to the full count, measured in GMT Greenwich Mean time. 

class Fourth: Mathematical Functions
The function has the following 18:
(1) ABS function: Math.Abs (the same as below), returns the absolute value of a number. 
(2) ACOs function: Returns the inverse cosine of a number with a result of 0~π radians (radians). 
(3) ASIN function: Returns the inverse chord value of a number, resulting in-Π/2~Π/2 radians. 
(4) Atan function: Returns the inverse tangent of a number, resulting in-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 (greater than or equal to) of a number. 
(7) Cos function: Returns the cosine of a number with the result of -1~1. 
(8) Exp function: Returns the value of the exponent of E (natural logarithm). 
(9) Floor function: Returns the maximum integer value (less than or equal to) of a number. 
log function: A natural logarithm function that returns the natural logarithm (e) value of a number. 
(one) Max function: Returns the maximum value of two digits. 
min Function: Returns the minimum value of two digits. 
POW function: Returns the value of a number. 
Random function: Returns a 0~1 value. 
round function: Returns the rounded value of a number with an integer type. 
sin function: Returns the sine of a number with the result of -1~1. 
sqrt function: Returns the square root value of a number. 
Tan function: Returns the tangent of a number. 

class Fifth: String Functions
The following 20 functions are included:
(1) Anchor function: Generates a link point (anchor) for use as a hyperlink. The Anchor function sets the name of the <a name...> link, and the other function link sets the URL address of the <a href=...>. 
(2) BIG function: Add the font to a number, the same as the <BIG>...</BIG> label results. 
(3) BLINK function: Causes the string to blink, the same as the <BLINK>...</BLINK> label result. 
(4) Bold function: Make the font bold, the same as the <B>...</B> label results. 
(5) Charat function: Returns a character specified in the string. 
(6) Fixed function: Sets the font to a fixed-width font, the same as the <TT>...</TT> label result. 
(7) FontColor function: Sets the font color, the same as the <font color=color> label results. 
(8) fontsize function: Sets the font size, the same as the <font size=n> label results. 
(9) indexof function: Returns the index of the first lookup in a string, starting from the left. 
() italics function: Make the font italic, same as the <I>...</I> label result. 
(one) LastIndexOf function: Returns the index of the first lookup in a string, starting from the right. 
length function: Returns the lengths of the strings. (without parentheses)
link function: Generates a hyperlink equivalent to the URL address of the set <a href=...>. 
SMALL function: Decrease the font size by one number and the same as the <SMALL>...</SMALL> label result. 
STRIKE function: Add a horizontal line to the middle of the text, the same as the <STRIKE>...</STRIKE> label result. 
() Sub function: The display string is the subscript (subscript). 
substring function: Returns the number of characters specified in the string. 
sup Function: The display string is the superscript word (superscript). 
() toLowerCase function: Converts a string to lowercase. 
() touppercase function: Converts a string to uppercase.

Reference:
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Https://zhidao.baidu.com/question/568123797.html

What are the JS functions