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The script in 1.HTML must be located between the <script> and </script> tags.
Scripts can be placed in the <body> and
2. If you need to access an HTML element from JavaScript, you can use the document.getElementById (ID) method
3. You can write content to HTML documents, including tags, via document.write (). Note that if document.write () is executed after the document has been loaded, the entire HTML document will be overwritten
4.JS comments through//and/**/two ways
5. Variable through VAR declaration, because JS is a weak type language, you can not specify the variable type.
var x=1 //number var x= "a"//String var x=true //boolean var x //x No value, undefined
6. Functions use function definition
Functions function name () {
function body;
}
7.var num=new Number ()//Declare a number object
Number.MAX_VALUE Maximum Value
Number.min_value Minimum value
Number.NaN Special non-numeric values
Number.negative_infinity Negative Infinity
Number.POSITIVE_INFINITY is Infinity
Number.toexponential () format numbers with exponential notation
Number.tofixed () using fixed-point counting method to format digital
Number.tolocalestring () A string that converts a number to a cost format
Number.toprecision () format a valid bit of a number
Number.tostring () converts-a number to a string
Number.valueof () returns the original value
8.var str = new string ()//Declare a String object
Str.substr (start,length): Extracts and returns a substring in Str. However, it does not modify the Str,start representation of the start position of the extraction, length represents the lengths, omitting length, then the extraction to the end.
Str.substring (From,to): Returns a substring of string strings, consisting of characters from between to, including characters located from, excluding characters located to. If the from>to, is automatically replaced after interception.
Str.tolowercase (): Converting strings to lowercase
Str.touppercase (): Converting strings to uppercase
Str.split (): Follow the specified symbol for string segmentation
Str.slice (): Same as substring () but flexible, allow negative values, similar to Array.slice ()
Str.concat (): String link, with Array.concat think, but with + number more convenient
Str.indexof (): Retrieves the character, returns the position where the character first appears
9.var date=new Date ()//Create a Dates Object
Some of the main methods are:
Date.get/setday ()//return/Set one day of the week (0~6),
Date.get/setfullyear ()//return/Set the year in system time
Date.get/setmonth ()//Returns/sets the Month field in the system time (0~11)
Date.get/setdate ()//return/Set one day of one months
Date.get/sethours ()//return/Set the hour field in the system time
Date.get/setminutes ()//Returns/sets the Minutes field in the system time
Date.get/setseconds ()//return/Set the seconds field in the system time
Date.get/settime ()//Returns/sets//Returns/sets the minute field in the system time
10.var arr=new Array ()///Create an Array object
Main properties: Arr.length//Returns the length of the array
Main methods:
POPs ()//deletes and returns the last element of the array, returning the value to the deleted element
Push ()///Add elements to the end of the array to return the length of the array
Shift ()///move the first element to the array, returning the value to the deleted element
Unshift ()///Insert an element at the head of the array to return the length of the array
Slice ()//returns part of the array, the argument can be negative, returns the captured array
Reverse ()//reverse the order in the array, returning the inverted array
Sort ()//array element ordering, specifying method
Concat ()//array connection, returns the concatenated array, does not change the original array
Join ()///To concatenate an array element to a specified character and return as a string
Splice ()//inserts, deletes, or replaces elements of an array.
ToString ()//converting an array to a string
11.Math is a native object
Math.Abs ()//return absolute value
Math.ceil ()///Up rounding
Math.floor ()//Country rounding
Math.Round ()//rounding
Math.randow ()//returns a random number
Math.max ()//returns a larger value
Math.min ()//returns a smaller value
Math.PI ()//constant PI
Math.pow () The Y-power of the//x
MATH.SQRT ()//Compute squared
12. Other
isNaN ()//To determine whether a numeric value, not a value returns True
parseint ()//cast to integer type
Parsefloat ()//cast to floating-point values
Alert ()//Warning
Confirm ()//Message Confirmation box
Prompt ()//Hint message box
document.write ()//writes content to an HTML document, overwriting the entire HTML document if the document content is written with that method after it has been loaded
document.getElementById ()//Get object by ID name
Document.getelementstagname ()//Gets the object by tag name, returns an array object
Document.getelementsclassname ()//Gets the object by class name and returns an array object
The above mentioned is the entire content of this article, I hope you can enjoy.
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