Java JavaScript (i)

1.JavaScript

A. Definition: JavaScript is a scripting language and a lightweight programming language

B. Implementation: ① directly through the Onxx attribute inside the tag to drive JS execution

<type= "button"  value= "Test"  onclick= "alert (' Hello ') ">

② introduction of external JS files--javascript file

<src= "My.js"></script>

③ can be placed in the <body> and

<type= "Text/javascript">    alert ("  Script"); </ Script >

2. Data type:

A. Data type: String (string), Number, Boolean (Boolean), arrays (array), objects (object), Null, Undefined

var num = 1; var str = "Hello"; var true ; var str1;

Note: The Var declaration variable is represented by a local variable, and the non-additive represents a global variable.

B. You can convert to string and Boolean by using new number:

var New Number (1); var New Number (true);    // result is 1 var New Number ("n");    // if the string is not a number, the result is Nan

C. You can convert to numeric and Boolean by using the new String:

var New String ("Hello"); var New String (n); var New String (ture);    // result is true

D. You can convert numbers and strings by using the new Boolean:

var New Boolean ("123");    // non-null is true var New Boolean (2);    // non-0 is true

Note: string: "" Null is false, non-NULL is True

Number: Not 0 is true,0 to False

The difference between e.null and undefined:

①undefined: Declares that the variable is not initialized

②null: When this element is not found in the document

F. Objects (object):

① initialization:

// Object Initialization method one: var person = {    userName:"Zhang San",    userpwd:"123",    userage: // Object Initialization mode two: var New  = "John Doe"= 18;

② Property Access:

// object's property access method one:    object name. property name; alert (user.username); // How to access the property of an object two:    object name ["Property name"]; Alert (user["attribute name"]);

G. Arrays

Statement:

var New Array ();    // declaration Method One var New Array (3); var nums = [1, 2, "Zhang San"];    // declaration Method Two var New Array ("Zhang San", "John Doe");    // declaration Method Three var New Array (new number (2));

3. Operators

A. Arithmetic operator: +-*/% + +--

B. Assignment operator: + = = *=/=%=

C. comparison operators: = = = = = = = = > < >= <=! =

①===: Indicates that the type and value are the same

②==: Represents the same value

The comparison of strings in JS is usually replaced by = =. Equal

D. Logical operator:&& | | !

E. Three-mesh operator:

var num = judgment expression? True execution expression: pseudo-execution expression

4. Judgment statement: If-else switch

5. Loop statement: While Do-while for For-each

 for (i = 0; i < i++) {    alert (i);}

 for inch names) {    document.write (Names[xindex]);}

6. Methods

A. Statement:

function Test (A, b) {    // declaration method one    return a +b;}var function () {    // declaration method two }varnewfunction () {    // declaration way Three })

Note: The function default return value is undefined (undefined)

function if you need to return a value, directly return

B. Access:

Test ();

7.String (String method is similar to Java, see API)

Str.substr (1,3)    // intercept element starting with subscript 1 to fetch 3 str.substring (1,3)    // intercept 1 to 2 elements (front closed) 

Note: The length of the JS string is an attribute, while in Java it is a method

8. Time (date)

varDate =NewDate ();//StatementvarDate =NewDate ("2015/01/01"); GetDay (); //the first day of the Week (0-6)GetDate ();//Day of January (1-31)GetMonth ();//month (0-11)getFullYear ();//returns the year as a four-digit numberGetHours ();//hours (0 ~ +)Getminutes ();//minutes (0 ~ $)Getseconds ();//number of seconds (0 ~ $)Getmilliseconds ();//milliseconds (0 ~ 999)GetTime (); //returns the number of milliseconds since January 1, 1970

Date.parse ("2015/01/01");    // specify the number of milliseconds for a date

9. Math (method similar to Java, see API)

10. Global functions

IsNaN ();    // Check if a value is a number Number ();    // converts the value of an object to a number String ();    // converts the value of an object to a string parseint ();    // parses a string and returns an integer parsefloat ();    // parses a string and returns a real number eval ();    // computes the JavaScript string and executes it as script code

11. Event (events)

A.ui Related: OnLoad, onunload, OnResize, onselect

B. Focus-Related: onblur, onfocus

C. Mouse related to scroll wheel: onclick, ondblclick, onmousedown, onmousemove, onmouseout, onmouseover, onmouseup

D. Keyboard-Related: onkeydown, onkeyup, onkeypress

E. Others: Onabord, onchange

12. Regular Expressions (REXEXP)

var regex =/^[a-z]$/g;    // /pattern/attributes var New REGEXP ("[A-Z]", "G");    // New RegExp (pattern, attributes); Regex.text (str);     // retrieves the value specified in the string. Returns TRUE or Falseregex.exec (str);    // retrieves the value specified in the string. Returns the found value and determines its location

Note: Str.match (regex);

Returns the result of matching a regular expression

If the global match, the returned array

If no match succeeds, NULL is returned

Java JavaScript (i)