JS Syntax Basics

1. Introduction method

<script type= "Text/javascript" > Specific code </script>

<script type= "Text/javascript" src= "Apple.js" ></script>

2. Case-sensitive

JavaScript language is strictly case-sensitive name name

3. How to Annotate

Comment Line

/*

Comment Multiple lines

*/

4. The end of the disposition number can be omitted (multiple expressions written in one line cannot be omitted)

var name= "Tom";

var age = 23;

5. Variable naming rules

Name composition: Letters, numbers, underscores, $

The first character of the start cannot be a number.

var $ = "China"; Yes, the jquery framework

var 9 = "Hello"; No

6. Global variables and local variables

① define "global variables" in JS and define them directly at any corner of the system (without using the var keyword)

② special cases, variables defined by Var outside the function are also "global"

Variables defined by var outside of nested functions in the ③ function can be used relative to this function

7. Connection Symbol +

　　When two parameters are numeric, do arithmetic operations; When two parameters one or two are string types, do the link operation

8. Break and Continue

Jump out of a loop and use it directly, if you need to jump out of multiple loops, use the following methods:

Waibian: For        (var i=0; i<10; i++) {            document.write (i+ "<br/>");            for (var j=100; j>=90; j--) {                //j==95 jumps outside the loop break                //if (j==95) {                    //break 2;    Do not use the number 2 (this usage is PHP's syntax rule)                //Break    Waibian;                }                                //j==95 jumps out of the "This" loop (let the outer for loop go directly to the next)                if (j==95) {                    continue Waibian;                }                document.write (j+ "<br/>");            }        }

9.switch

A switch condition can be a value, an expression, and a case can be followed by a constant, a variable, an expression