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A two-point description of the JavaScript concept:
1, it is a network scripting language, used to embed in HTML pages for Web development purposes.
2. It has nothing to do with Java's half-dime relationship.
How to use
1. How to embed in HTML
1-1, the script is written in the <body> tag in the bottom, that is, </body> above.
1-2, defined directly in the page: <script type= ' text/javascript ' > Script code </script>
1-3, as a file is loaded: <script src= "js file path" ></script>
1-4. Writing specification:
1-4-1, add a semicolon at the end of each executable statement (;)
1-4-2, note indenting and adding spaces to improve code readability
1-4-3, single-line comment//Multiline comment with/* content */
2. Variables
The scope of a JavaScript variable is broken down by a function block (that is, by a pair of curly braces {}), for, if, and so on, which is not a scoping criterion for scopes:
Variables outside of function, whether global or local, are in effect in all the function of the current page
Variables within function, local variables are only valid in the current function. Global variables are global in effect.
2-1. Global variable: name = ' value ';
2-2, local variables: var name = ' value ';
3. String method
>var name = ' value ' #定义一个字符串 with one space on each side
>name.trim () #去除字符串两边的空格
"Value"
>name.charat (1) #按照索引1获取字符串的第2个值 (index 0 is the 1th value)
"V"
>name.substring (1,3) #按照索引范围获取一个子序列字符串
"VA"
>name.indexof (' u ') #查找字符串中字符的索引值
4
>name.length #获取字符串长度
7
4. Arrays (list)
>var list = [] or var list = Array () #声明数组
#添加
>list.push (1) #追加数字1
>list.push (' abc ')
[1, "ABC"]
>list.unshift (0) #在最前面插入
[0, 1, "ABC"]
>list.splice (2,0, ' def ') #在索引值2前面插入
[0, 1, "Def", "ABC"]
#获取 (remove)
>list.pop () #获取最后一个值
"ABC"
>list
[0, 1, "Def"]
>list.shift () #获取第一个值
0
>list
[1, "Def"]
List.splice (index,n) #获取从index处开始的N个元素
>list.splice (a)
["Def"]
>list
[1]
#其他
>list=[1, 2, 3]
>list.slice (0,2) #切片
[1, 2]
>list2=[3,4,5]
>list3=list.concat (LIST2) #合并
[1, 2, 3, 3, 4, 5]
>list3.reverse () #翻转
[5, 4, 3, 3, 2, 1]
>list3.join ('_') #字符串化
"5_4_3_3_2_1"
>list3.length #长度
6
5. Functions (function)
Functions are divided into:
5-1. Basic functions: Functions that need to be called through an event to execute
Example:
<script type= "Text/javascript" > Function Foo (ARG) {console.log (ARG); } </script>5-2. Self-executing function: function that executes automatically when the page frame is loaded
Example:
<script type= "Text/javascript" > (function Foo (ARG) {console.log (ARG); }) (' Test ') </script>6. Circulation
The loop is divided into:
6-1, for: Loop code block a certain number of times
Example:
for (var i=0; i<5; i++) {x = ' the number is ' + i; Console.log (x); }6-2. For/in: Looping through the properties of an object
Example:
var list = [1,2,3,4] for (var i in list) {x = "the number is" + list[i]; Console.log (x); }6-3, while: loops the specified block of code when the specified condition is true
Example:
var list = [1,2,3,4] while (list.length>1) {List.pop () Console.log (list); }6-4, Do/while: First execute the code once, if the condition is true, it will repeat the loop
Example:
var list = [1,2,3,4]; do{List.pop (); Console.log (list); }while (list.length>1);7. Exception Handling
Grammar:
try{
Run the code here
}catch (Err) {
Handle the error here
}finally{
Non-mandatory, if any, executes this block of code, whether or not it is an error
}
Example:
try{var n = m; }catch (Err) {Console.log (err); }finally{Console.log (' Code is End '); }part of the blog content and ideas organized from Wu Jianzi blog .
This article from "A rookie on the Sky" blog, please be sure to keep this source http://rmeos.blog.51cto.com/761575/1743900
HTML Basics (JavaScript)
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