Summary of several methods of traversing json to obtain data

Json is widely used in Web development. As a carrier of data transmission, how to parse the data returned by Json is very common. Here are four ways to parse Json:

Part 1

var list1 = [1,3,4]; 
alert(list1[1]); 
var list2 = [{"name":"leamiko","xing":"lin"}]; 
alert(list2[0]["xing"]) 
alert(list2[0].xing) 

Part 2

var value = { 
  "china":{ 
    "hangzhou":{"item":"1"}, 
    "shanghai":{"item":"2"}, 
    "chengdu":{"item":"3"} 
  }, 
  "America":{ 
    "aa":{"item":"1"}, 
    "bb":{"item":"2"}  
  }, 
  "Spain":{ 
    "dd":{"item":"1"}, 
    "ee":{"item":"2"}, 
    "ff":{"item":"3"}  
  } 
}; 
  
for(var countryObj in value) 
{ 
  document.write(countryObj + ":<br />") 
  // It's useless for(var cityObj in value.countryObj) 
  for(var cityObj in value[countryObj]) 
  { 
    document.write('  ' + cityObj + "<br />"); 
    for(var itemObj in value[countryObj][cityObj]) 
    { 
      document.write("   "+ itemObj + value[countryObj][cityObj][itemObj] +"<br />")  
    } 
  }  
}

Explanation:

countryObj is an attribute of value object, value [countryObj] is the attribute value of value object, here is an json object such as b, value [countryObj] [cityObj] is the attribute value of b object of josn object, which is also an json object, so value [countryObj] [cityObj] ["item"] can get the value that json object temporarily becomes c, or value [countryObj] [cityObj].

In a word, it is crucial to distinguish between json and array.

Part 3

var value2 = { 
  "china":[ 
    {"name":"hangzhou", "item":"1"}, 
    {"name":"shanghai", "item":"2"}, 
    {"name":"sichuan", "item":"3"} 
  ], 
  "America":[ 
    {"name":"aa", "item":"12"}, 
    {"name":"bb", "item":"2"} 
  ], 
  "Spain":[ 
    {"name":"cc", "item":"1"}, 
    {"name":"dd", "item":"23"}, 
    {"name":"ee", "item":"3"} 
  ] 
};<BR>  
for (var countryObj in value2) 
{ 
  document.write(countryObj + ":<br />")  
  for (var cityObj in value2[countryObj]) 
  { 
    // Can be used document.write(" " + value2[countryObj][cityObj].item + "<br />"); 
    document.write(cityObj + " " + value2[countryObj][cityObj]["name"] + "<br />" );  
  } 
}

Explanation:

countryObj is the property name of the value2 object, value2 [countryObj] is the property value of the value2 object, in this case it is an array, cityObj is an element of the array, and it is another json object, so value2 [countryObj] [cityObj] ["name"] accesses the property value of the name of the object, or it can be accessed through value2 [countryObj] [cityObj]. name.

Part 4

var value2 = { 
  "china":[ 
    {"name":"hangzhou", "item":"1"}, 
    {"name":"shanghai", "item":"2"}, 
    {"name":"sichuan", "item":"3"} 
  ], 
 
  "America":[ 
    {"name":"aa", "item":"12"}, 
    {"name":"bb", "item":"2"} 
  ], 
  "Spain":[ 
    {"name":"cc", "item":"1"}, 
    {"name":"dd", "item":"23"}, 
    {"name":"ee", "item":"3"} 
  ] 
}; 
   
  for (var countryObj in value2) 
  { 
    document.write(countryObj + ":<br />")  
    //document.write(" " + value2[countryObj].length); 
    for (var i = 0;i < value2[countryObj].length; i++) 
    { 
      document.write(" " + value2[countryObj][i]["name"] + "<br />");  
    } 
  }

Explanation:

countryObj value2 object property name, value2 [countryObj] property value, in this case an array, value2 [countryObj]. length array length, value2 [countryObj] [i] array entries = = json object.

value2 [countryObj] [i] ["name"] takes the value of name, or value2 [countryObj] [i]. name can be used to take the value of name.

When a person can't find a way out, the best way is to do what he can do well at present to the extreme, so that no one can reach it.