JS built-in objects

String object: A String object that provides properties and methods for manipulating a string.

Array object: Arrays object that provides properties for array manipulation and is illegal.

Date object: A DateTime object that can obtain the system's datetime information.

Boolean object: A Boolean object, a Boolean variable that is a Boolean object.

Number object: A numeric object, a numeric variable is a numeric object.

Math object: A Mathematical object that provides properties and methods for mathematical operations.

String object:

Length: string lengths.

toLowerCase (): Converts the letters in a string to lowercase.

toUpperCase (): Converts the letters in a string to uppercase.

CharAt (): Returns the character at the specified position.

IndexOf (): Returns the position where the specified substring first appears in the original string. If not found, returns-1.

LastIndexOf (): Returns the location of the last occurrence of the specified substring in the original string. If not found, returns-1.

SUBSTR (): Extracts the specified number of characters from the starting index number in the string.

SUBSTRING (): Extracts the characters between two specified index numbers in a string (the characters in the last position are not extracted).

Split (): Splits the string into an array.

Array object:

1. An array variable is an array object.

2. Properties and methods:

Length: The number of array members.

Join (): merges the array elements. Put all the elements of the array into a string. element is delimited by the specified delimiter.

Reverse (): Reverses the order of the elements in the array.

Shift (): the head popup element. Deletes and returns the first element of the array. (unlike delete array[i]; Delete can only delete the element value, the occupied space is still, the total length is unchanged. ）

Unshift (): The head is pressed into the element. Adds one or more elements to the beginning of the array and returns the new length.

Push (): the tail is pressed into the element. Adds one or more elements to the end of the array and returns the new length.

Pop (): Tail popup element. Deletes and returns the last element of the array.

Date object:

1. Create a Date object:

1 //(1). Create a Date object with the current time without any parameters2 varDateobj =NewDate ();3 4 //(2). Create a Date object with a specified timestamp5 //      time stamp refers to the total number of milliseconds since GMT January 1, 1970 0:0 0 seconds (Beijing time January 1, 1970 8:0 0 seconds) until now6 varDateobj =NewDate (60000);7 8 //(3). Create a Date object of the specified day9 varDateobj =NewDate ("2016/11/04 12:21:00");Ten  One //(4). Specify multiple numeric parameters A //      The order is: year, month, day, time, minute, second. The year, the month and the day are necessary.  - varDateobj =NewDate (2016 + 100, 11, 24, 10, 20, 0);//creates a Date object with a datetime of November 24, 2116 12:21 0 seconds

2. Properties and methods:

getFullYear (): Gets the four-bit year.

GetMonth (): Gets the month (0-11).

GetDate (): Gets the number (1-31).

GetHours (): Gets the number of hours (0-23).

Getminutes (): Number of minutes (0-59).

Getseconds (): Number of seconds (0-59).

Getmilliseconds (): MS (0-999).

GetDay (): Week (0-6,0 for Sunday).

GetTime (): Timestamp. Millisecond value from GMT January 1, 1970 to the present.

Math Object

1. The Math object is a static object. When using the Math object, you do not need to wear an instance.

2. Properties and methods:

Math.PI: Pi.

Math.Abs (): The absolute value of the returned number.

Math.ceil (): Rounding up. (integer plus 1, decimal removed). such as: Math.ceil (10.2) = = 11

Math.floor (): Rounding down. (remove decimals directly). such as: Math.floor (9.88) = = 9

Math.Round (): Rounds the number to the nearest integer.

Math.pow (x, y): power function. X is the Y-square.

MATH.SQRT (): To find the square root.

Math.random (): Returns a random floating-point number between 0 and 1.

Number Object

1. A numeric variable is a numeric object.

2. Properties and methods:

ToFixed (): Converts a numeric value to a string and rounds it, preserving the decimal number of the specified digits.

JS built-in objects