ast-delete-object^4.2.1

Installation

Quick Take

Examples

• Delete empty objects throughout a tree
• Delete every object that contains the requested pair
• Delete a matching object nested under another object
• Delete the root object when it contains the requested key-value pairs
• Keep whitespace-only objects when hungry matching is disabled
• opts.hungryForWhitespace
• opts.matchKeysStrictly
• Delete an object that contains additional keys

Purpose

It deletes objects in AST if all given keys-value pairs are matched.

API — deleteObj()

The main function deleteObj() is imported like this:

It’s a function which takes three input arguments:

None of the input arguments will be mutated by this program, we have unit tests to prove that.

The Optional Options Object has the following shape:

Here are all defaults in one place for copying:

The function will return the clone of first input argument with relevant elements deleted.

API — defaults

You can import defaults:

It's a plain object:

The main function calculates the options to be used by merging the options you passed with these defaults.

API — version

You can import version:

API — types

This package is written in TypeScript and exports the following types:

import type { JsonArray, JsonObject, JsonValue, Opts } from "ast-delete-object";

opts.matchKeysStrictly

If you want the search to be strict, that is to require the key set to match exactly, use options object, matchKeysStrictly: true:

import { deleteObj } from "ast-delete-object";
let res = deleteObj(
  [
    "elem1",
    {
      findme1: "zzz",
      findme2: "yyy",
      somethingelse: "qqq", // <--- this key will block deletion
    },
    "elem2",
  ],
  {
    findme1: "zzz",
    findme2: "yyy",
  },
  {
    matchKeysStrictly: true, // <--- strict matching
  },
);
console.log("res = " + JSON.stringify(res, null, 4));
// => nothing changes!
// [
//   'elem1',
//   {
//     findme1: 'zzz',
//     findme2: 'yyy',
//     somethingelse: 'qqq'
//   },
//   'elem2'
// ]

In example above, object was not deleted because strict matching ignored it because of unrecognised key somethingelse.

opts.hungryForWhitespace

This is a library to deal with AST’s, and they usually have lots of white space. Often there are many elements that contains only spaces, tabs or line breaks. Sometimes you want to pretend that those elements containing white space don’t exist, so deletion is more aggressive regarding the white space.

For example, notice how looking for a blank plain object also catches other objects that contain only empty space:

import deleteObj from "ast-delete-object";
let res = deleteObj(
  [
    { a: "\n" },
    {
      key3: "val3",
      key4: "val4",
    },
    { b: "   " },
    { c: "" },
  ],
  {},
  { matchKeysStrictly: false, hungryForWhitespace: true },
);
console.log("res = " + JSON.stringify(res, null, 4));
// =>  [{
//      key3: 'val3',
//      key4: 'val4'
//    }]

Context

Originally, this program was created to help us delete unused CSS (as objects) from parsed HTML (AST tree) in email-comb. Since then, we’ve rewritten email-comb to process the code without parsing, without AST. email-comb became faster by magnitude (milliseconds instead of seconds/minutes).

Changelog