@anypoint-web-components/anypoint-selector/src/AnypointSelection.js

Port of iron-selector that works with ES6 classes. Manages a list of elements that can be selected.

/**
 * Port of `@polymer/iron-selector/iron-selection.js`.
 */
export class AnypointSelection {
  /**
   * @param {!Function} selectCallback
   * @suppress {missingProvide}
   */
  constructor(selectCallback) {
    this.multi = false;
    this.selection = [];
    this.selectCallback = selectCallback;
  }

  /**
   * Retrieves the selected item(s).
   *
   * @return {*} Returns the selected item(s). If the multi property is true,
   * `get` will return an array, otherwise it will return
   * the selected item or undefined if there is no selection.
   */
  get() {
    return this.multi ? this.selection.slice() : this.selection[0];
  }

  /**
   * Clears all the selection except the ones indicated.
   *
   * @param {any[]?} excludes items to be excluded.
   */
  clear(excludes) {
    this.selection.slice().forEach((item) => {
      if (!excludes || excludes.indexOf(item) === -1) {
        this.setItemSelected(item, false);
      }
    });
  }

  /**
   * Indicates if a given item is selected.
   *
   * @param {*} item The item whose selection state should be checked.
   * @return {boolean} Returns true if `item` is selected.
   */
  isSelected(item) {
    return this.selection.indexOf(item) >= 0;
  }

  /**
   * Sets the selection state for a given item to either selected or deselected.
   *
   * @param {*} item The item to select.
   * @param {boolean} isSelected True for selected, false for deselected.
   */
  setItemSelected(item, isSelected) {
    if (item !== null) {
      if (isSelected !== this.isSelected(item)) {
        // proceed to update selection only if requested state differs from
        // current
        if (isSelected) {
          this.selection.push(item);
        } else {
          const i = this.selection.indexOf(item);
          if (i >= 0) {
            this.selection.splice(i, 1);
          }
        }
        if (this.selectCallback) {
          this.selectCallback(item, isSelected);
        }
      }
    }
  }

  /**
   * Sets the selection state for a given item. If the `multi` property
   * is true, then the selected state of `item` will be toggled; otherwise
   * the `item` will be selected.
   *
   * @param {*} item The item to select.
   */
  select(item) {
    if (this.multi) {
      this.toggle(item);
    } else if (this.get() !== item) {
      this.setItemSelected(this.get(), false);
      this.setItemSelected(item, true);
    }
  }

  /**
   * Toggles the selection state for `item`.
   *
   * @param {*} item The item to toggle.
   */
  toggle(item) {
    this.setItemSelected(item, !this.isSelected(item));
  }
}