JS。 将事件属性类型分配给变量

Question

Not sure how to formulate a question, need to assign something like a type of event to a variable and then use it. For instance:

mx = ('ontouchstart' in document.documentElement) ? event.changedTouches[0].pageX : event.pageX;

then:

function fn(e) {
  return mx - elem1.getBoundingClientRect().left;
}

that is e -event object goes to mx and returns the assigned earlier event type (so that мх is either e.changedTouches[0].pageX or e.pageX ).

Is it possible to do that? (otherwise, have to check for the support of ontouchstart each px of mouse move...)

Answer 1

If you do not want to do the if check on every iteration, than just defined the function with the version you want.

var fn = (function () {
  if ('ontouchstart' in document.documentElement){
     return function(event){
         return event.changedTouches[0].pageX - elem1.getBoundingClientRect().left
     }
  } else {
     return function(event){
         return event.pageX - elem1.getBoundingClientRect().left
     }
  }
}());