We often use javascript Of json.

First of all javascript Of json What is string ,json The string belongs to javascript An object of , Objects with keys and values .

The general format is ：

a = {

a1 : 1,

a2 : 'abc',

a3 : 'abc',

a4 : [1,2,3],

a5 : function(){console.log(12)}

};

We read this json The way is through for in Loop to traverse ;

Use json The advantage of string is that the data in the database can be read out and saved in one time in advance json In the form of , And then through javascript To read what belongs to , This can greatly reduce the number of requests to the server , Increase the loading efficiency of the front page .

We're traversing json There are a lot of problems when I'm going to work , The problem I have today is that we put json When the key value of a string is written as a number , In the mainstream browser traversal time will not follow our output json The structure of the output , It's output in the order of numbers from small to large . however ie8 The following browsers will output in the order we output .

for example ：

a = { 
'1' : 1,
'5' : function(){console.log(12)},
'2' : 'abc',
'4' : [1,2,3],
'3' : {'5' : 'abc', '6' : 'bcd'},
};

adopt for in loop

for(var i in a){
console.log(a[i]);
}

chrome,firefox Wait for the browser output ：1,abc,Object { 5="abc", 6="bcd"},[1, 2, 3],function();

ie8 And the following browsers ：1,function(),abc,[1, 2, 3],Object { 5="abc", 6="bcd"};

There are two ways to solve such problems ：

First of all ： It is to change the key value of a number into a string, including letters or underscores ;

second ： That's the solution ie The compatibility of , By traversing first json Then put the key values in an array , And then through the array sorting to loop the array to get json Data in .

Specific code ：

var arr = [],sortNumber = function (a,b){

return a - b;
};
for(var i in a){
  arr[arr.length] = a[i];
}

arr.sort(sortNumber);

for(var x = 0; x < arr.length; x++) {

console.log(a[arr[x]]);

}

In this way, the data read by the browser will be consistent , One drawback is that this will not be exported according to our output json Format output , It just solves the problem of browser compatibility .

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