Detailed explanation of usage examples of $.getJSON asynchronous and synchronous requests

A previous function wanted to call the return value of the previous function, but its return value was always empty. Later, after looking through some information, I realized that asynchronous requests were causing trouble. I won’t go into details, but look at the example:

function get_no_order_array() { 
  var order_info = show_order(); 
  var order = []; 
  
  $.getJSON("../JSON/customers.json", function (date) { 
 
    date["man"].forEach(function (person) { 
      if (order_info.k_obj[person] == undefined) { 
        order.push(person); 
      } 
    }) 
  }); 
 
  return order; 
}

Later I found that the printed array order was always empty. The following is the corrected code:

function get_no_order_array() { 
  var order_info = show_order(); 
  var order = []; 
  $.ajaxSettings.async = false;//在执行之前加$.ajaxSettings.async = false;  (同步执行) 
  $.getJSON("../JSON/customers.json", function (date) { //<span style="line-height: 1.5;">$.getJSON不懂的话可以看一下我之前的博客，或是专门学习一下  “JSON”</span>

date["man"].forEach(function (person) { 
      if (order_info.k_obj[person] == undefined) { 
        order.push(person); 
      } 
    }) 
  }); 
  $.ajaxSettings.async = true;//执行你的代码之后及时恢复为$.ajaxSettings.async = true； （异步执行） 
  return order; 
}

Add $.ajaxSettings.async = false; before the loop to indicate synchronous execution, so that it will be executed in order.

Solution to the problem of data confusion caused by executing multiple $.getJSON() at the same time

Add $.ajaxSettings.async = false; before execution (synchronous execution)

Execution Your code will be restored to $.ajaxSettings.async = true in time; (asynchronous execution)

Otherwise, it will affect the code in other places that needs to be executed asynchronously.

$.ajaxSettings.async = false;

$.getJSON(url, data, function(data){ });

$.getJSON(url, data, function(data){ });

$.getJSON(url, data, function(data){ });

......

$.ajaxSettings.async = true;

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