1) The $.parseJSON method returns a string, not a JSON object.
2) To convert a string into an object, it is easy to think of the eval method in JS. In fact, it is possible, but you need to add parentheses. Such as var js="{"PageIndex":"1"}";var obj=eval("(" js ")");. However, using eval is unsafe because it can compile any js code.
3) Download a JSON parser, because it only recognizes JSON text. This is safer. The JSON official website provides such a script. Address: http://www.JSON.org/json2.js. It is relatively simple to use. After introducing the file, such as: JSON.parse($("#ctl00_ContentPlaceHolder1_hfSearch").val().toString()).
4) When using the JSON.parse method or the $.parseJSON method, note that the name and value of the JSON data are enclosed in double quotes. For the $.parseJSON method, the JSON string must be enclosed in single quotes. Up and then convert, for the JSON.parse method, it is not necessary. What a fucking waste of time.
Pay attention to these tips to avoid many detours when operating JSON data.