Ajax and JSON data interactive storage

This time I will bring you the interactive storage of Ajax and JSON data. What are the precautions for interactive storage of Ajax and JSON data? The following is a practical case, let's take a look.

Data storage is the core function of

JavaScript. This is an easily confusing issue in the early stages of learning. It is not the kind of eye-catching special effects such as page sliding, slide show, fade in and out, etc. Properly storing data helps us organize the structure and makes it easier for applications to access the content later. JavaScript provides a variety of data storage methods. It is an evolutionary model from basic to future trends:

XML stands for extensible markup language and is a relatively flexible data format. Many applications store data. Everyone likes to use it. Its structure is like HTML, and it also contains elements, tags and attributes. The model is the same. One of its major advantages is that it is an extensible format, and you are not restricted to a certain preset data structure; and it also conforms to the DOM standard, and the data obtained using AJAX calls is just like parsing HTML, through The corresponding DOM methods and attributes parse it:

<ingredient>
<prison>
<name>apple</name>
<color>red</color>
</prison>
<prison>
<name>tomato</name>
<color>red</color>
</prison>
<prison>
<name>peach</name>
<color>pink</color>
</prison>
<prison>
<name>pitaya</name>
<color>green</color>
</prison>
</ingredient>

But a serious flaw of XML is that it cannot be used for cross-domain Aiax calls, which means that the XML data of each Ajax call must be consistent with the execution call The script is in the same domain name, otherwise the request will fail.

HTML storage is also similar, it is the easiest to combine with Ajax. The important factor in using this data format is speed. The HTML code snippet can be directly output to the DOM without being parsed on the client, so we do not need to write additional JavaScript code to parse HTML.

<ul>
<li><a href="boke.js">apple:red</a></li>
<li>tomato:red</li>
<li>peach:pink</li>
<li>piyata:green</li>
</ul>

Let’s talk about its shortcomings. The data it stores may be mixed with HTML code, so maintainability is reduced. In addition, when writing processing code, developers may need to make some fine control measures on the server side.

The following is How to use JavaScript for data storage, step by step...

Variables

JavaScript is the most basic data storage method. It accepts strings, values, Boolean, etc. The core content is its scope issue.

Performance issues related to variables:

After the variable is declared, it will be cached in the JavaScript file, so it is within the scope They can be used repeatedly. The cost of obtaining variables is minimal. As long as the number of times the data is used is greater than 1, it should be stored in the variable.

Array

Arrays, like ordinary arrays, associative arrays and

multidimensional arrays, are all lists of elements. This form is a variety of data storage A very flexible one. Mastering the most basic form of arrays will also be of great benefit to the use of other complex forms. Accessing array elements is common to basic interactive code. In view of the importance of arrays as a data storage type, JavaScript provides a large number of exclusive methods for array interaction operations: the

.join() method can specify a certain character as a connector for each element in the array; The slice() method can output elements within a certain range in the array; the shift() and unshift() methods are used to remove or add elements at the head of the array respectively; the pop() method is used to remove and return elements in the array. The last element; the concat() method is used to splice multiple arrays into one array, depending on the order of the parameters; the sort() method can arrange the elements of the array in alphabetical order or a custom order, but it will only be based on the first Character sorting is generally wrong.

Object

When the data becomes more complex and difficult to manage, I will choose to convert the array into an object. Because the way objects are stored is more readable.

//对象数据存储
var meatball = {
bread:"wang",
meat :"li",
cheese : "zhang"
};
//返回对象的bread 
alert(meatball.bread);

The impact of objects on efficiency

The above code has only one layer, but it can be infinitely nested. Objects can better organize code and improve modularity. At the same time, though, there are performance and maintainability tradeoffs to consider, as it requires looking for one of these three. If

Object-oriented programming technology is used, and the nesting reaches 3 levels or more, performance problems will occur; but this is not the case when used on the server side, so front-end developers must decide when to use object-oriented Programming technology.

JSON

JSON是一种易于同jacascript 集成的数据格式，它通常是在用JavaScript调用外部服务器时使用的。JSON数据存放于独立的文件中，而且通常位于另一台完全不同的服务器上。它现在是最常见的一种调用API服务时所使用的数据格式，人们之所以选中它，是因为此格式非常易于阅读。起初，JSON格式是作为一种XML格式的替代方案而出现的，但很快它就在数据交换领域占据了主流的地位。它是一种轻量级的数据格式，易于通过远程Ajax调用进行跨域名访问。尽管JavaScript对JSON格式的解析提供了原生的支持，但它还是一种独立于平台的格式，客户端与服务器端在数据交换时都可以使用。

由于JSON格式具备跨域名访问的能力，所以为了防止一切恶意行为，我们务必只使用从可信的数据源中获取JSON。

这是一个 Salad.json 数据文件：

//ajax JSON Salad
var ingredient = {
"fruit":[
{
"name" : "apple",
"color" : "green"
},
{
"name" : "tomato",
"color" : "red"
},
{
"name" : "peach",
"color" : "pink"
},
{
"name" : "pitaya",
"color" : "white"
},
{
"name" : "lettuce",
"color" : "green"
}
]
};

JSON最常见的用途就是配合API调用，在于API为基础的网络程序开发环境中，使用何种后端语言进行开发，数据格式都无需改变。

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