Differences between JSON. parse () and eval () in javascript to parse json _ javascript skills

This article mainly introduces JSON in javascript. the difference between parse () and eval () in json Parsing is described in detail. The operation skills of json format data are described in detail. the difference between parse () and eval () in json Parsing is as follows. parse () and eval () parse json. We will share this with you for your reference. The details are as follows:

JSON (JavaScript Object Notation) is a lightweight data format that uses a completely language-independent text format and is an ideal data exchange format. JSON is a Javascript native format, which means processing JSON data in javascript

Basic Format:

varjsonData='{"data1":"Hello,","data2":"world!"}'

Call method jsonData. data1, jsonData. data2

Store a lot of json data into Arrays

var jsonData=[ {"name":"LiLei","age":19,"sex":"male"}, {"name":"HanMei","age":18,"sex":"famale"}]

Call MethodJsonData [0]. name, jsonData [1]. sex

In general, json is relatively easy to understand and use, but there are many traps at the same time, if you do not pay attention to it, it is easy to fall.

Json Parsing Method

Json is parsed in two ways: eval () and JSON. parse (). The method is as follows:

var jsonData = '{"data1":"Hello,", "data2":"world!}';var evalJson=eval('('+jsonData+')');var jsonParseJson=JSON.parse(jsonData);

In this way, the json string jsonData is converted into a JSON object.

The differences between the two are as follows:

Var value = 1; var jsonstr = '{"data1": "hello", "data2": ++ value }'; var data1 = eval_r ('+ jsonstr +'); console. log (data1); // The value is 2var data2 = JSON. parse (jsonstr); console. log (data2); // Error

The result of the control output table is displayed. The first eval () is successfully executed, and the second error is reported. As shown in the preceding example,When parsing a string, eval will execute the code in the string (the consequence is rather bad ),In the preceding example, the original value is changed due to parsing a json string using eval.

High Performance Javascript (site: http://www.jb51.net/books/36680.html) book that points out:

Warning JSON and eval:It is very dangerous to use eval in code, especially when using it to execute third-party JSON data (which may contain malicious code), try to use the JSON. parse () method to parse the string itself. This method can capture syntax errors in JSON and allow you to input a function to filter or convert the parsing results. If this method is supported by Firfox 3.5, IE8, and Safari 4 native. Most javascript class libraries contain JSON Parsing Code that directly calls the native version. Without native support, it will call a slightly less powerful non-native version for processing.