JavaScript basic syntax

1. Variables

JavaScript is a weakly typed language, there is no type variable, that is, a variable can store any type of data

Define variables to be defined with Var

Example: Var x=3; var x= "string";

Note: Both single and double quotes in JavaScript can define a string, undefine is a constant value that is not initialized by a variable in JS

2. Statements

Roughly the same as Java

Note: null is false in JavaScript, non-null is True

3. Functions

JavaScript does not have a type, the function does not involve return type and parameter type

Use function to define functions

Called in <script></script> when the function is called

Note:<script></script> is the code range for JavaScript

Example: General functions

<script>    function  Show (x, y)    {    }</script>

Dynamic functions: That is, parameters and function bodies can be passed in as variables.

var New Function("x", "Y"; " Alert (x+ "" +y); ");

Anonymous functions: Can be used as a way to handle an event

var function (){}

Note: A function can also have a return value, and if a function without () is assigned a value, it is the processing of the assigned function, and if so, the return value of the assigned function.

You can use functions to create objects, object-oriented thinking, code examples:

<script>    function person (name, age)    {        this. Name = name;          this. Age = Age ;    }     var New Person ("Lisi");     = "Boy"    function()    {        alert ("Walk");    } </script>

Note: There are two ways to invoke the top object's own property, which can be called through., or by p["property name", what is the difference between the two?

P.name This method is only suitable for a single call, p["name"] this way can implement bulk call

For example, p has more than one property, the property name of P is read out in an array m, when the bulk call can be used p["m[i]" this way to achieve

　　　　

JavaScript basic Syntax