vant-fork/es/utils/event.js

Lightweight Mobile UI Components built on Vue

import { isServer } from './';
export var supportsPassive = false;

if (!isServer) {
  try {
    var opts = {};
    Object.defineProperty(opts, 'passive', {
      get: function get() {
        /* istanbul ignore next */
        supportsPassive = true;
      }
    });
    window.addEventListener('test-passive', null, opts);
  } catch (e) {}
}

export function on(target, event, handler, passive) {
  if (passive === void 0) {
    passive = false;
  }

  !isServer && target.addEventListener(event, handler, supportsPassive ? {
    capture: false,
    passive: passive
  } : false);
}
export function off(target, event, handler) {
  !isServer && target.removeEventListener(event, handler);
}