JS related knowledge

1.$(function() {})

      $(function() {}) yes jquery There is a way of writing , Similar to the original js Medium DOMContentLoaded event . He was $(document).ready(function() Abbreviation .

      When is this function executed ？

      He is in DOM It is executed after loading , That is, all the pages html label （ Including pictures, etc ） All loaded , The browser has responded , all dom The tree is all displayed on the browser interface （ It's all kinds of element labels ）, Everything is all set. （ The picture , These static resources such as audio and video have not been loaded ） This function starts to execute .

2.JSON.stringify()

       JSON.stringify() Method is used to JavaScript Value to JSON character string . His grammar is JSON.stringify(value[, replacer[, space]]), among value For the data that needs to be transformed ;replacer Optional. . The function or array used to convert the result . If replacer For the function , be JSON.stringify This function will be called , And pass in the key and value of each member . Use the return value instead of the original value . If this function returns undefined, Then exclude members . The key of the root object is an empty string ："". If replacer Is an array , Only the members with key values in the array are converted . Members are converted in the same order as keys in the array ;space It's also an option , Is to add indentation to the text 、 Space and newline , If space It's a number , The return value text is indented by a specified number of spaces at each level , If space Greater than 10, The text is indented 10 A space .space You can also use non numbers , Such as ：\t.

We usually use JSON.stringify(value) To quickly convert data into json character string .

3.JSON.parse()

      JSON.parse() Method to convert data to JavaScript object . His grammar is JSON.parse(text[, reviver]), among text It's a required option , He must be an effective JSON character string , If it is not, it will report an error ;reviver Optional. , Is a function of the conversion result , This function will be called for each member of the object to be converted .

4.JS Get information about the current web page

    stay WEB In development , It's often used javascript To get the url Website information , Here are the small chestnuts for each part

    Let's take a chestnut URL= http://test.com/testPath?parm=123

     4.1 window.location.href Get the entire URL For the string

           var tem= window.location.href; return ：http://test.com/testPath?parm=123

     4.2 window.location.protocol obtain URL Part of the agreement

           var tem= window.location.protocol; return ：http:

     4.3 window.location.host obtain URL The host part of

           var tem= window.location.host;  return ：test.com

     4.4 window.location.port To obtain and URL Associated port number

           var tem= window.location.port; return ： Null character ( This is because the default 80 port ( Even if you add it manually :80), So the return value is not the default 80 It's an empty character )

     4.5 window.location.pathname To obtain and URL The path part of

           var tem= window.location.pathname; return ：/testPath

     4.6 window.location.search obtain href The part of the attribute that follows the question mark

           var tem= window.location.search; return ：?parm=123 

     4.7 window.location.hash obtain href Attribute in "#" Later parameters

           var tem= window.location.hash; return ： Null character