Development tools and key technology: Adobe Dreamweaver & amp; & JavaScript
Author: WeiYongGui
Writing time: April 24th, 2020,
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A, Array Array
The introduction of 1, an array
- an array of objects (built-in objects)
- similar to it and our common object function, also is used to store some values
- different is common object using a string as the attribute name
And as index operation element array is to use Numbers to
- index: starting from 0 index of integer is
- an array of storage performance is better than ordinary objects, we often use in the development of an array to store some data
(1) to create an Array object: var arr=new Array ();
(2) to add elements in the array (array syntax: [index]=value)
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(3) read the elements in the array (array syntax: [index]) if read index does not exist, are not returned an error but undefined
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(4) to obtain the length of the array, you can use the length of the attribute to get (syntax: array. Length)
For a continuous array, using the length can access to the length of the array (the number of elements)
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For the continuous array, use access to the array's largest length (index + 1)
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Try not to create an array of discontinuous
(5) modified length
- if you modify the length is more than the original length, the part will be more free
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- if you modify the length is less than the original length, the more part will be deleted
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2, array literals
(1) use the literal to create an array (syntax: [])
(2) using a literal creating arrays, can be specified in the create the array elements in the
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(3) an array of values can be any data type, object contains
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(4) can be stored in the array function
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(5) the two-dimensional array
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3, the method of array
Such as: (1) create the array (var arr=[" Ming ", "little red", "little orange"])
(2) to connect two or more arrays, and returns the result of [methods: concat ()]
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Series (3) all the elements in the array into a string, the element with a specified delimiter separated by [methods: the join ()]
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(4) [methods: push ()]
- this method can add one or more elements to the array at the end of the array and returns the new length, such as:
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- can add elements as a method of parameter passing, so these elements will be automatically added to the end of the array, such as:
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- this method will be an array of new length as the return value is returned
(5) [methods: pop ()] this method can remove the last element of an array, and will be deleted elements as the return value is returned
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(6) [methods: unshift ()]
- start to add one or more elements to an array, and returns a new array length
After inserting elements - forward edge, index of other elements will in turn adjustment
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(7)/methods: the shift () you can delete the first element of the array, and will be deleted elements as the return value is returned
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4, array traversal: so-called iterate through group, is to remove all elements in the array to
Method one:
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Method 2:
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A, Date Date
The Date object (built-in objects) in JS use the Date object to represent a time
1, create a Date object (var Date=new Date ()) , if the time to use the constructor to create a Date object, will be encapsulated in the current code execution time,
2, create a specified time object, in the constructor is passed a time string as a parameter,
Var date=new date (" 2020-03-23 12:34:12 ");
3, [methods: getDate ()] - access to the current date object days
4, [methods: getDay ()]
- access to the current date of the week, will return a value of 0 ~ 6 (0 said Sunday, 1 said on Monday,... , 6 said Saturday)
5, [methods: getMonth ()]
- for current month of the date object, returns a value of 0 ~ 11 (0 said in January, February 1,... Said, 11 December)
6, [methods: getFullYear ()] - access to object to four digit year of return
7, [methods: getHours ()] - for current date object hours
8, [methods: getMinutes ()] - for current date object minutes
9, [methods: getSeconds ()] - gets the current number of seconds a date object
10, [methods: getTime ()]
Object - to get the current date timestamp
- a timestamp, refers to from Greenwich mean time on January 1, 1970, 0 0 0 seconds
Cost to the current date (the number of milliseconds (1 second=1000 milliseconds)
- the underlying computer used in the preservation time is timestamp
Second, Math object
1, Math object and other objects, it is not a constructor, it belongs to a utility class don't have to create the object, it encapsulates the mathematics related attributes and methods, such as: Math, said PI PI (3.14159) is approximately equal to
2, Math. Abs (x) - returns the absolute value of a number, Math. Sin (x) - returns the sine of a number,
3, Math. Ceil () - can be carried out on a number of integer upwards, small digital so long as has the value will automatically into 1
4, Math. Floor () - can be carried out on a number of downward integer, decimal portion will be down
5, Math. The round () - a number can be rounded integer
6, Math. The random ()
- can be used to generate a random number between 0 and 1
Math. The random ()
- can be used to generate a random number between 0 and 10 (integer)
Math. Round (Math. The random () * 10)
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