strategyFunction(extent, resolution) {
    // extents may be passed in different worlds, to avoid endless loop we use only one
    let realWorldExtent = extent.slice();
    if (this.projection_ && this.getSource().getWrapX()) {
      wrapExtentX(realWorldExtent, this.projection_);
    }
    if (this.loadedExtent_) {
      if (
        approximatelyEquals(this.loadedExtent_, realWorldExtent, resolution)
      ) {
        // make sure result is exactly equal to previous extent
        realWorldExtent = this.loadedExtent_.slice();
      } else {
        // we should not keep track of loaded extents
        this.getSource().removeLoadedExtent(this.loadedExtent_);
      }
    }
    return [realWorldExtent];
  }
Strategy function for loading features based on the view's extent and
resolution.
@param {import("../extent.js").Extent} extent Extent.
@param {number} resolution Resolution.
@return {Array<import("../extent.js").Extent>} Extents.