Running JavaScript Code from Python

Using the execjs library; install it with:

pip install PyExecJS

How to use it:

1. Pass in a shorter JavaScript script directly

   import execjs
   execjs.eval("new Date")
   ## Return value: 2018-04-04T12:53:17.759Z
   execjs.eval("Date.now()")
   # Return value: 1522847001080  # Note that the return value has 13 digits, unlike Python's time.time()
   

2. Compile a large JS file and call functions in it

   ## The JS we handle in production runs to hundreds or thousands of lines, too long to paste here. Let's look at the example given in the source code:
     ctx = execjs.compile("""
        function add(x, y) {
                return x + y;
           }
   """)
     ctx.call("add", 1, 2)  # The first argument, "add", is the string name of the JS function; the arguments that follow are the actual arguments
     # Return value: 3
   

3. The environment that runs the JS

   execjs.get().name
   ## On Windows it defaults to JScript; for Node.js it is Node.js (V8)
   

Common problems:

1. Syntax errors The IE JavaScript engine is used by default; to fix this you need to install nodejs. Download it here: [Node.js (nodejs.org)](https://nodejs.org/zh-cn/). After installing it you have to restart PyCharm before it is detected.

2. jQuery is undefined Run the following in the python project directory:

   npm i jsdom
   npm i jquery
   

   Also add the following before the JS file to be executed:

   var jsdom = require('jsdom');
   const { JSDOM } = jsdom;
   const { window } = new JSDOM();
   const { document } = (new JSDOM('')).window;
   global.document = document;
   var $ = jQuery = require('jquery')(window);