January 25 JavaScript Introduction and syntax

First, JavaScript introduction

(1), Usage:

(1), head inside//head inside main put function

(2), body inside (the body within the most rigorous)

(3),

(2), 3 common dialog boxes

Alert () Warning dialog box, which is the function of a warning dialog to pop up. The dialog box pops up before executing.

Confirm () Determines the dialog box, the function is to pop up a selection of OK dialog box, after clicking OK, it returns True, click Cancel to return flase, available variables to accept.

The prompt () function pops up a dialog box that allows you to enter content. All the strings entered from the box

Note: All of the above three omit window.

Second,JavaScript syntax

(1), Variable type:javascript variable type only one , var. var is a generic mutable type.

(2), Data type: Integer, Decimal, String, Boolean (similar to C #)

(3), type conversion: automatic conversion and casting, generally with cast.

1. How to convert other types to digital type:
parseint ("string")--turns the string into an integral type
Parsefloat ("string")--turns the string into a decimal number

2. How can I tell if a variable is a number?
var a = IsNaN (b); IsNaN--->is not a number

A is true is not a number

A is false is a number

(4), operator

Math operators: +,-*,/,%, + + 、--(7)

Relational operators:>, <, >=, <=, = =,! = (6)

Logical operators: | |, &&,!

Other operators: + =,-=, *=,/=,%=,?:

(5), statement

Order, branching, looping.

1. Branch: If.....else

2. Loop: For

(6), array

1. Definition:

var a=new Array (); Its length is dynamically variable and can be placed in any type of element.

2. Method:

A.sort (); sort an array, Sort by the first character.

A.reverse (); flips an array.

(7), function:

Four elements: function name, input, output, function body

1. Define the function:

function add (formal parameter)

{function body;}

// function name is add , the input is the form of a parameter, and the return value can be a var type or return value.

2, Function call: ( function does not call will not execute)

Add (actual parameter);

Note: JavaScript is case sensitive.

January 25 JavaScript Introduction and syntax