undo-manager/lib/undomanager.js

Simple undo manager to provide undo and redo actions in JavaScript applications.

/*
Simple JavaScript undo and redo.
https://github.com/ArthurClemens/JavaScript-Undo-Manager
*/

(function () {
  'use strict';

  function removeFromTo(array, from, to) {
    array.splice(
      from,
      !to ||
        1 +
          to -
          from +
          (!((to < 0) ^ (from >= 0)) && (to < 0 || -1) * array.length),
    );
    return array.length;
  }

  let UndoManager = function () {
    let commands = [],
      index = -1,
      limit = 0,
      isExecuting = false,
      callback;

    /**
     * Executes a single command.
     * @property {object} command        - Command
     * @property {function} command.undo - Undo function
     * @property {function} command.redo - Redo function
     * @property {string} action         - "undo" or "redo"
     */
    function execute(command, action) {
      if (!command || typeof command[action] !== 'function') {
        return this;
      }
      isExecuting = true;

      command[action]();

      isExecuting = false;
      return this;
    }

    return {
      /**
       * Adds a command to the queue.
       * @property {object} command           - Command
       * @property {function} command.undo    - Undo function
       * @property {function} command.redo    - Redo function
       * @property {string} [command.groupId] - Optional group id
       */
      add: function (command) {
        if (isExecuting) {
          return this;
        }
        // if we are here after having called undo,
        // invalidate items higher on the stack
        commands.splice(index + 1, commands.length - index);
        commands.push(command);

        // if limit is set, remove items from the start
        if (limit && commands.length > limit) {
          removeFromTo(commands, 0, -(limit + 1));
        }

        // set the current index to the end
        index = commands.length - 1;
        if (callback) {
          callback();
        }
        return this;
      },

      /**
       * Pass a function to be called on undo and redo actions.
       * @property {function} callbackFunc - Callback function
       */
      setCallback: function (callbackFunc) {
        callback = callbackFunc;
      },

      /**
       * Performs undo: call the undo function at the current index and decrease the index by 1.
       */
      undo: function () {
        let command = commands[index];
        if (!command) {
          return this;
        }

        const groupId = command.groupId;
        while (command.groupId === groupId) {
          execute(command, 'undo');
          index -= 1;
          command = commands[index];
          if (!command || !command.groupId) break;
        }

        if (callback) {
          callback();
        }
        return this;
      },

      /**
       * Performs redo: call the redo function at the next index and increase the index by 1.
       */
      redo: function () {
        let command = commands[index + 1];
        if (!command) {
          return this;
        }

        const groupId = command.groupId;
        while (command.groupId === groupId) {
          execute(command, 'redo');
          index += 1;
          command = commands[index + 1];
          if (!command || !command.groupId) break;
        }

        if (callback) {
          callback();
        }
        return this;
      },

      /**
       * Clears the memory, losing all stored states. Resets the index.
       */
      clear: function () {
        let prev_size = commands.length;

        commands = [];
        index = -1;

        if (callback && prev_size > 0) {
          callback();
        }
      },

      /**
       * Tests if any undo actions exist.
       * @returns {boolean}
       */
      hasUndo: function () {
        return index !== -1;
      },

      /**
       * Tests if any redo actions exist.
       * @returns {boolean}
       */
      hasRedo: function () {
        return index < commands.length - 1;
      },

      /**
       * Returns the list of queued commands.
       * @param {string} [groupId] - Optionally filter commands by group ID
       * @returns {array}
       */
      getCommands: function (groupId) {
        return groupId ? commands.filter(c => c.groupId === groupId) : commands;
      },

      /**
       * Returns the index of the actions list.
       * @returns {number}
       */
      getIndex: function () {
        return index;
      },

      /**
       * Sets the maximum number of undo steps. Default: 0 (unlimited).
       * @property {number} max - Maximum number of undo steps
       */
      setLimit: function (max) {
        limit = max;
      },
    };
  };

  if (
    typeof define === 'function' &&
    typeof define.amd === 'object' &&
    define.amd
  ) {
    // AMD. Register as an anonymous module.
    define(function () {
      return UndoManager;
    });
  } else if (typeof module !== 'undefined' && module.exports) {
    module.exports = UndoManager;
  } else {
    window.UndoManager = UndoManager;
  }
})();