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This article operating environment: windows7 system, javascript1.8.5 version, Dell G3 computer.

What are the javascript functions?

JavaScript built-in functions (built-in functions, built-in keywords)

The built-in object of js is included with js, which encapsulates some commonly used methods. Commonly used js built-in objects are: String,Date,Array,Math, etc.

Js built-in functions are built into the browser kernel and can be used directly without any library introduction. Javascript built-in functions can be divided into five categories:

1. General function

2. Array function

3. Date function

4. Mathematical function

5. String function

The first category: regular functions

Includes the following nine functions:

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

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

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

(4) eval function: the result of evaluating the expression.

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

(6) parseFloat function: converts a string into a symbol point number.

(7) parseInt function: converts the string to integer numeric form (decimal can be specified).

(8) prompt function: displays an input dialog box that prompts you to wait for user input.

The second category: array functions

Includes the following four functions:

(1) join function: converts and concatenates all elements in the array into a string.

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

(3) reverse function: reverses 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, 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 represents Monday, and 6 represents Saturday.

(3) getHours function: returns the "hour" part of the date, with a value of 0023.

(4) getMinutes function: returns the "minute" part of the date, with a value of 0059. See the above example.

(5) getMonth function: returns the "month" part of the date, with a value of 011. Where 0 is January, 2 is March, and 11 is December. See the previous example.

(6) getSeconds function: returns the "second" part of the date, with a value of 0059. See the previous example.

(7) getTime function: returns the system time.

(8) getTimezoneOffset function: returns the time difference of this area (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, 99 in 1999.

(10) parse function: returns the number of milliseconds (local time) from 00:00 on January 1st, 1970.

(11) setDate function: sets the "day" part of the date, with a value of 0,31.

(12) setHours function: sets the "hour" part of the date, with a value of 0,23.

(13) setMinutes function: set the "minutes" part of the date, with a value of 0059.

(14) setMonth function: sets the "month" part of the date, with a value of 011. Where 0 means January, and 11 means December.

(15) setSeconds function: sets the "second" part of the date, with a value of 0059.

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

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

(18) toGMTString function: converts the date into a string, which is GMT Greenwich mean time.

(19) setLocaleString function: converts the date into a string, local time.

(20) UTC function: returns the number of milliseconds from 00:00 on January 1, 1970, calculated in GMT Greenwich mean time.

The fourth category: mathematical functions

There are 18 functions:

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

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

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

(4) atan function: returns the inverse tangent of a number, and the result is-π / 2 ~ π / 2 radians.

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

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

(7) cos function: returns the cosine of a number, and the result is-1x 1.

(8) exp function: returns the multiplier value of e (natural logarithm).

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

(10) log function: a natural logarithmic function that returns the natural logarithm (e) of a number.

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

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

(13) pow function: returns the multiplier value of a number.

(14) random function: returns a random value of 0: 1.

(15) round function: returns the rounded value of a number whose type is an integer.

(16) sin function: returns the sine of a number, and the result is-1 to 1.

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

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

The fifth category: string functions

Includes the following 20 functions:

(1) anchor function: generates a link point (anchor) for hyperlink. The name of the link point set by the anchor function and the URL address set by another function link.

(2) big function: add the font to the first number, and. The label results are the same.

(3) blink function: make the string flicker, and. The label results are the same.

(4) bold function: make the font bold, and. The label results are the same.

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

(6) fixed function: set the font to a fixed width font, and. The label results are the same.

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

(8) fontsize function: sets the font size, which is the same as the result of the label.

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

(10) italics function: make the font italic, and. The label results are the same.

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

(12) length function: returns the length of the string. (no parentheses)

(13) link function: generates a hyperlink, which is equivalent to the set URL address.

(14) small function: reduce the font by one number, and. The label results are the same.

(15) strike function: add a horizontal line in the middle of the text, and. The label results are the same.

(16) sub function: displays the string as subscript (subscript).

(17) substring function: returns a few characters specified in the string.

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

(19) toLowerCase function: converts a string to lowercase.

(20) toUpperCase function: converts a string to uppercase.

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