How to conditionally filter an array of objects that includes duplicates in Javascripts

Question

I have an array of objects like following, some commands share the same text:

const Commands=[
{
  id: "id1",
  text: "read",
  message: "read",
},
{
  id: "id2",
  text: "read",
  message: "read a book",
},
{
  id: "id3",
  text: "sleep",
  message: "sleep",
},
{
  id: "id4",
  text: "help",
  message: "help",
},
{
  id: "id5",
  text: "help",
  message: "command help",
},
]

I want to filter this array out based on the user input message. Also, for the commands that have the same text, I only want the first one (or the default one). For example, if the user input ["read a book"], the result would be

[
{
  id: "id2",
  text: "read",
  message: "read a book",
},
{
  id: "id3",
  text: "sleep",
  message: "sleep",
},
{
  id: "id4",
  text: "help",
  message: "help",
},
]

if the user input ["read a message"], which does not exist in the array, the default one will be returned, the result would be

[
{
  id: "id1",
  text: "read",
  message: "read",
},
{
  id: "id3",
  text: "sleep",
  message: "sleep",
},
{
  id: "id4",
  text: "help",
  message: "help",
},
]

Here is my JavaScripts/TypeScripts,

const defaultReadText =
    Commands.find(
      (command) => command.message === userReadMessage
    )?.text ?? "read"
  const defaultReadMessage =
    Commands.find(
      (command) => command.message === userReadMessage
    )?.message ?? "read"

const defaultHelpText =
    Commands.find(
      (command) => command.message === userHelpMessage
    )?.text ?? "help"
  const defaultHelpMessage =
    Commands.find(
      (command) => command.message === userHelpMessage
    )?.message ?? "help"

 const enabledCommands =
    Commands.filter(
        (command) =>
          (command.text === defaultReadText &&
            command.message === defaultReadMessage) ||
          command.text != defaultReadText
      )?.filter(
        (command) =>
          (command.text === defaultHelpText &&
            command.message === defaultHelpMessage) ||
          command.text != defaultHelpText
      )

I wonder if there is better way to solve this?

Nina Scholz · Accepted Answer · 2021-12-07 21:09:11Z

1

You could group by text and take the object for a matching message.

const
    filter = (array, message) => Object.values(array.reduce((r, o) => {
        if (!r[o.text] || o.message === message) r[o.text] = o;
        return r;
    }, {})),
    commands = [{ id: "id1", text: "read", message: "read" }, { id: "id2", text: "read", message: "read a book" }, { id: "id3", text: "sleep", message: "sleep" }, { id: "id4", text: "help", message: "help" }, { id: "id5", text: "help", message: "command help" }];

console.log(filter(commands));
console.log(filter(commands, "read a book"));
console.log(filter(commands, "read a message"));

.as-console-wrapper { max-height: 100% !important; top: 0; }

A chainable approach with reduce

const
    filter = message => (r, o) => {
        if (r[r.length - 1]?.text === o.text) {
            if (o.message === message) r[r.length - 1] = o;
        } else {
            r.push(o);
        }
        return r;
    },
    commands = [{ id: "id1", text: "read", message: "read" }, { id: "id2", text: "read", message: "read a book" }, { id: "id3", text: "sleep", message: "sleep" }, { id: "id4", text: "help", message: "help" }, { id: "id5", text: "help", message: "command help" }];

console.log(commands.reduce(filter(), []));
console.log(commands.reduce(filter("read a book"), []));
console.log(commands.reduce(filter("read a message"), []));

.as-console-wrapper { max-height: 100% !important; top: 0; }

edited Dec 7, 2021 at 21:09

answered Dec 7, 2021 at 20:31

Nina Scholz

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2 Comments

GLP Over a year ago

Thank you so much for the quick response. But the chainable one seems work if the array is sorted by the text field. If I move the object of "read a book" to the end, it won't work, still return both "read" object. Also, I think I may need to add another boolean field to define with command is the default one, otherwise, whichever is the first one in the sorted array will be considered as the default.

Nina Scholz Over a year ago

right. it's up to you.

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