JavaScript Basics Points

JavaScript role:
1, the interactive effect of the page
2. Form Verification

JavaScript consists of:
1, ECMAscript---Core
2. DOM---Document Object model documents
3. BOM---Browser object model
window--window
history--history
location--Address bar (URL)
document--page (body) DOM

How does JavaScript work?
1. Get the Element (tag) obtained by ID, class, tag
2. Operation Contents
3. Operation Properties
4. Operation Style
5. Create a delete tag
6. Operation Events

JavaScript language (routines):
1. Comments, keywords, identifiers, constants
Single-line Comment
/*
Multi-line comments
*/
Identifier rules: Letters, numbers, underscores, $ symbols, etc. 4 components, numbers can not be used as a name
Constant: 10 1000 "Hello"
2. Variables, data types
variables:
Define and assign values: var variable name = value; name = value;
JavaScript Data type (6 types):
1, number (int (integer, no decimal)/float (decimal))
2, string "string" number of strings added stitching
3, Boolean Boolean type: Not true is false true (True) False (false)
4 NULL null value does not point to
5, undefined no definition
6. Object objects
(An array is part of an object)
3. Operators
1, arithmetic operator: +-*/% Remainder {+ +) self-increment-self-increment self-decrement before after + + + + + + + + + + + + + + + + + + +
Assignment operator: = + = =
2. Relational operators: > < >= <=! = = = value Size comparison (judging) = = = value size and data type comparison
3, logical operator:&&//or! Return: Back
4, ternary operator: expression
4. Control statements
Sequential structure
Branching selection Structure: if
else if
Switch: is a match for the specific value, no break is found in the next case, until the last case has penetration
Break: Jump out of

String to Character: parseint (content)

Loop structure: while () Dead Loop Do{}while () for ()
Two types of cycle usage scenarios:
For: The number of known loops
While: satisfies a conditional termination loop

Break: In the loop, switch inside has to use out of the current layer of the loop to terminate the loop
Continue: Use out of the loop inside the loop to enter the next cycle

for (var i=0; i<0;i++) {

}
for (1. initialization; 2. Condition judgment; 3. Change of State) {
4. Code of execution
}

while (1 expression 2. Code executed) {
}
1.
Judging whether an expression is ture

do{

}while (expression);
If expression 1 establishes execution code 1 otherwise executes code 2

if (expression 1) {
Code to execute
}else (expression 2) {
Code to execute
}
If set to execute if, do not establish execute else

switch (matching value) {

Case "value":

Code

Break

Default

Code

Break

}

Note: When no break is found, continue to find break

5. Arrays
6. Methods (Functions)
function Definition :
1.function Method Name (parameter list 1, parameter List 2 ... ）{
Code Collection
}
2.var Method name = function (argument list) {}
function (method) does not execute without calling

Method Invocation: Method Name (parameter list 1, parameter List 2 ... ）


Class, Object

Console.log (console print)

How to use javascript:
1. Write directly in the tag, the value of the event attribute (the common value is the method name)
<div onclick= "alert (123)" > Popup 123</div>
2. In the HTML file in the form of a label, the sign is script
<script type= "Text/javascript" >
JS Code
</script>
3. External references are displayed in the HTML file as a label, and the signature is script
<script type= "Text/javascript" src= "" ></script>

JS three kinds of pop-up windows:
alert ();---alarm window has no return value
Confirm ();---Select Window has return value Boolean type
Prompt ();---input window has a return value user input

JavaScript Basics Points