How to use inline JavaScript inside a snippet to process variables?

Question

I need to process $TM_SELECTED_TEXT. The processing is more than RegEx. Can I use inline JavaScript inside keybindings.json?

Current code:

[
    {
        "key": "cmd+k t",
        "command": "editor.action.insertSnippet",
        "when": "editorTextFocus",
        "args": {
            "snippet": "${TM_SELECTED_TEXT /_/g}"
        }
    }
]

I couldn't find any step by step guide to use inline JavaScript.

Answer 1

There is no built-in way to run javascript in a snippet transform. An extension I wrote, Find and Transform, allows you to use javascript string and math operations (and more) to create replacement text.

For example, this keybinding (in keybindings.json):

{
  "key": "alt+y",                   // whatever keybinding you want
  "command": "findInCurrentFile",
  "args": {
    // "preCommands": "cursorHomeSelect",    // if necessary
    // "find": "<text or regex>",            // not necessary here

    "replace": [
      "$${",            // syntax to start a js operation
        
      // note the ticks around the variable, so it is seen by js as a string
      // must use semicolons at the end of each statement

      "let myVar = '${selectedText}'.substring(2).toLocaleUpperCase();",
      "myVar += ' Hello';",
        
      "return myVar;",                               // must use return
        
      "}$$"                             // syntax to close js operation
    ],
    // "isRegex": true,                           // not necessary here
    "restrictFind": "selections" 
  }
}

would replace the selected text with the string operation <the selected text>.substring(2).toLocaleUpperCase(). You can do any other string operations you want. Or Math operations if your selected text was a Number.

You can also use other types of variables, like https://code.visualstudio.com/docs/editor/variables-reference#_predefined-variables and more.