JS-JavaScript Study Notes (1): javascript Study Notes

JS-JavaScript Study Notes (1): javascript Study Notes
JavaScript


1. document Output: document. write () can output characters, expressions, html tags, functions


2. Any type and string addition will be converted to the string type.
For example, var I = 5; var j = "5"; var k = I + j; Result: k = 55


3. Operator priority (from high to low)
Arithmetic Operators-> comparison operators-> logical operators-> "=" value assignment operators. If operations at the same level are performed in the left-to-right order, the multi-layer brackets are left-to-right.


4. Events:
Onclick,
Onmouseover,
Onmouseout move with the mouse,
Onfocus gets focus,
Onblur loses focus,
Onselect selected,
The onchange text box is changed,
Onload loading,
Onunload uninstall
5. built-in objects


Date object,
Get/setTime (); time
Get/setDate (); Date
GetDay (); week
String object,
CharAt (index); get the character at the specified position;
IndexOf (substring, startPos); returns the position where the specified string appears for the first time;
Split (separator, limit); string split into character Arrays
Substring (startPos, endPos); extract the string that the string is intermediary between two downlink
Subsrt (startPos, length); extract the specified number of strings starting from the startPos position in the string


Math object,
Ceil (x); rounded up
Floor (x); rounded down
Round (x); rounding
Random (); random Number


Array object,
Concat (array1.... arrayN); array connection
Join (separator); specify a separator to connect to an array element
Reverse (); reverse the order of array elements
Slice (start, end); returns the specified element from an existing array
Sort (method function); sorts arrays in a certain order
Example:
<Script type = "text/javascript">
Function sortNum (a, B ){
Return a-B;
// In ascending order, such as descending order, convert "a-B" to "B-"
}
Var myarr = new Array ("80", "16", "50", "6", "100", "1 ");
Document. write (myarr + "<br> ");
Document. write (myarr. sort (sortNum ));
</Script>

6. browser objects

** Browser Object Model (BOM)

(1). window object

(2). javascript Timer
A. Timer var I = setInterval (Code, interaction time); During execution, the code is executed at the specified time after loading the page.
B. Cancel the time clearIntercal (I );
C. The setTimeout (Code, latency time) timer executes an expression once after the specified delay after loading.

D. Cancel the clearTimeout timer (ID value returned by setTimeout)

(3). The History Object-the history object records the pages (URLs) that the user has browsed, and allows the browser to move forward and backward in similar navigation.
A. window. history. [attribute | method]
B. Return the number of URLs in the browser history list.

C. method: back (), load the previous URL in the History list, which is equivalent to go (-1); forward () loads the next URL in the History list, which is equivalent to go (1 ); go (number-the relative location of the URL to be accessed in the list) loads the page specified in the History List

(4). Location object -- location is used to obtain or set the URL of the form, and can be used to parse the URL.

(5). the Navigator object-the Navigator object contains information about the browser, which is usually used to detect the version of the browser and the operating system.

(6). screen Object -- screen object is used to obtain the user's screen information.

7. DOM (Document Object Model) Document Object Model-Defines standard methods for accessing and processing HTML documents. DOM presents HTML documents as a tree (node tree) with elements, attributes, and text ).

(1). getAttribute (name) method-get the attribute value through the attribute name of the element node.
Syntax:
ElementNode. getAttribute (name)
Note:
1. elementNode: The Element Node obtained by getElementById () and getElementsByTagName.
2. name: attribute name of the element node to be queried
(2). setAttribute () method-Add a new attribute with a specified name and value, or set an existing attribute to a specified value.
Syntax:
ElementNode. setAttribute (name, value)
Note:
1. name: name of the property to be set.
2. value: the property value to be set.
Note:
1. Set the specified attribute to the specified value. If no property with the specified name exists, this method creates a new property.
2. Similar to the getAttribute () method, the setAttribute () method can only call functions through element node objects.
(3) visible area size of the browser window
A Practical JavaScript solution for different browsers:
Var w = document.doc umentElement. clientWidth
| Document. body. clientWidth;
Var h = document.doc umentElement. clientHeight
| Document. body. clientHeight;
(4) web page size scrollHeight
Browser compatibility
Var w=document.doc umentElement. scrollWidth
| Document. body. scrollWidth;
Var hsf-document.doc umentElement. scrollHeight
| Document. body. scrollHeight;
Note: Case Sensitive
ScrollHeight and scrollWidth can also obtain the actual height and width of the content in the Dom element.


(5) webpage size offsetHeight
OffsetHeight = clientHeight + scroll bar + border.
Browser compatibility
Var w = document.doc umentElement. offsetWidth
| Document. body. offsetWidth;
Var h = document.doc umentElement. offsetHeight

| Document. body. offsetHeight;

Reference: http://www.imooc.com/learn/10

Learning Website: http://www.dreamdu.com/javascript/core/

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