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JSON: JAvaScript Object Notation (JavaScript object notation)
JSON is the syntax for storing and exchanging textual information. Similar to XML.
JSON is smaller, faster, and easier to parse than XML.
JSON instance{"sites""name": "Huazhong University of Science and Technology", "URL": "www.hust.edu.cn" "name": "Google", "url": " www.google.com "" name ":" Weibo "," url ":" Www.weibo.com " }]}The JSON text format is syntactically identical to the code that creates the JavaScript object.
Because of this similarity, the JavaScript program can use the built-in eval () function to generate native JavaScript objects with JSON data without a parser.
2. JSONGrammarJSON syntax is a subset of JavaScript syntax.
2.1 JSON Syntax rulesJSON syntax is a subset of the JavaScript object notation syntax.
Data in name/value pairs
Data is separated by commas
Curly braces Save Object
Save array in brackets
The writing format for JSON data is: name/value pairs.
Name/value pairs include the field name (in double quotation marks), followed by a colon, and then the value:
" name" : Huazhong University of Science and Technology " equivalent to this JavaScript statement:name = " Beginner's tutorial "
2.3 JSON ValueThe JSON value can be:
The JSON number can be integer or float:{ "age": -
2.5 JSON ObjectThe JSON object is written in curly braces ({}):
An object can contain multiple name/value pairs:{ "name":"Huazhong University of Science" , "url":" www.hust.edu.cn" }
2.6 JSON ArrayThe JSON array is written in brackets:
An array can contain multiple objects
{"sites""name": "Huazhong University of Science and Technology", "URL": "www.hust.edu.cn" "name": "Google", "url": " www.google.com "" name ":" Weibo "," url ":" Www.weibo.com " }]}The JSON Boolean value can be True or false:{ "flag":true }
2.8 JSON NULLJSON can set a null value:{ "root":null }
2.9 JSON using JavaScript syntaxJSON uses JavaScript syntax, so you can work with JSON in JavaScript without the need for additional software.
With JavaScript, you can create an array of objects and assign values like this:
var sites = [ "name": "Huazhong University of Science", "url": "Www.hust.edu.cn" }, "name": "Google "," url ":" Www.google.com " }, " name ":" Weibo "," url ":" Www.weibo.com " }];
The first item in an array of JavaScript objects (the index starts at 0):
Sites[0]. Name; What's returned is: Huazhong University of Science and Technology
You can modify the data like this: sites[0]. Name="Tsinghua University ";
2.10 JSON FileSyntax Example:{ "name":"runoob", "alexa":10000, "site":null }
The JSON object is written using the curly braces ({}).
An object can contain multiple key/value (key/value) pairs.
Key must be a string, and value can be a valid JSON data type (string, number, object, array, Boolean, or null).
A colon (:) split is used in key and value.
Each key/value pair uses commas (,) to split.
3.1 Accessing object valuesUse the dot number (.) To access the value of the object:
1<body>2 3<p> You can use the dot number (.) To access the value of the JSON object:</p>4 5<p id= "Demo" ></p>6 7<script>8 9 varmyObj, X;TenMYOBJ = {"Name": "Runoob", "Alexa": 10000, "Site":NULL }; Onex =Myobj.name; Adocument.getElementById ("Demo"). InnerHTML =x; - -</script> the -</body>
Use the brackets ([]) to access the value of the object:
<p> You can also use brackets ([]) to access the value of the Josn object: </p><p id= "Demo" ></p><script>var= MYOBJ = {"Name": "Runoob", "Alexa": 10000, "site":null= myobj["name"];d Ocument.getelementbyid ( "Demo"). InnerHTML = x; </script>Use For-in to loop the properties of an object:
1 var myObj = {"Name": "Runoob", "Alexa": 10000, "site":null }; 2 for inch MYOBJ) {3 document.getElementById ("Demo"). InnerHTML + = x + "<br>"; 4 }When you for-in the properties of a loop object, use the brackets ([]) to access the value of the property:
1 var myObj = {"Name": "Runoob", "Alexa": 10000, "site":null }; 2 for inch MYOBJ) {3 document.getElementById ("Demo"). InnerHTML + = Myobj[x] + "<br>"; 4 }< Span class= "Hl-code" >json object can contain another JSON object: Span class= "hl-brackets" > < Span style= "font-size:16px" >
1 myObj = {2 "name": "Runoob",3 "Alexa": 10000,4 "Sites": {5 "site1": "www.hust.edu.cn",6 "Site2 ":" m.hust.edu.cn ",7 " Site3 ":" c.hust.edu.cn "8 }9 }Use dot number (.) or the brackets ([]) to access the nested JSON object.
3.4 Modifying valuesx = myObj.sites.site1; // or x = myobj.sites["Site1"];
3.5 Delete Object Properties= "www.google.com"; use brackets ([]) to modify the value of the JSON object: myobj.sites["site1"] = "www.google.com";
3.6 the difference between a JSON object and a JSON string:Delete keyword to remove the properties of the JSON object: Delete myObj.sites.site1; use brackets ([]) to remove the properties of the JSON object: Delete myobj.sites["site1"]
JSON object
var str2 = { "name": "Asan", "Sex": "man" };
JSON string
var str1 = ' {' name ': ' Deyuyi ', ' sex ': ' Man '} ';
JSON Learning notes (i)
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