Function onRef

src/index.ts:288–310

(el: HTMLElement | null)

  };

  const onRef = (el: HTMLElement | null) => {
    // "inline" ref functions are called twice on render, once with null then again with DOM element
    // ignore null here
    if (el === null) return;
    set((state, props) => {
      // if the same DOM el as previous just return state
      if (state.el === el) return state;

      const addState: { cleanUpTouch?: () => void } = {};
      // if new DOM el clean up old DOM and reset cleanUpTouch
      if (state.el && state.el !== el && state.cleanUpTouch) {
        state.cleanUpTouch();
        addState.cleanUpTouch = void 0;
      }
      // only attach if we want to track touch
      if (props.trackTouch && el) {
        addState.cleanUpTouch = attachTouch(el, props);
      }

      // store event attached DOM el for comparison, clean up, and re-attachment
      return { ...state, el, ...addState };
    });
  };

  // set ref callback to attach touch event listeners
  const output: { ref: typeof onRef; onMouseDown?: typeof onStart } = {