javascript - 当我编写脚本时，它显示 ReferenceError : theWidth is not defined

Question

这是我的代码:

$(window).load(function() {
  var theImage = $('ul li img');
  var theWidth = theImage.width();
  //wrap into mother div
  $('ul').wrap('<div class="gallery-slide" />');
  //assign height width and overflow hidden to gallery-slide
  $('.gallery-slide').css({
    width: function() {
      return theWidth;
    },
    height: function() {
      return theImage.height();
    },
    position: 'relative',
    overflow: 'hidden'
  });
  //get total of image sizes and set as width for ul
  var totalWidth = theImage.length * theWidth;
  $('ul').css({
    width: function() {
      return totalWidth;
    }
  });
});

$('ul li img').each(function(intIndex) {
  $(this).nextAll('a').bind("click", function() {

    if ($(this).is(".next")) {
      $(this).parent('li').parent('ul').animate({
        "margin-left": (-(intIndex + 1) * theWidth)
      }, 1000);
    } else if ($(this).is(".previous")) {
      $(this).parent('li').parent('ul').animate({
        "margin-left": (-(intIndex - 1) * theWidth)
      }, 1000);
    } else if ($(this).is(".startover")) {
      $(this).parent('li').parent('ul').animate({
        "margin-left": (0)
      }, 1000);
    }
  }); //close .bind()
}); //close .each()

上面是我的代码，它抛出错误theWidth is not Defined。

Answer 1

JavaScript has function-level scope(before ECMAScript 6), if a variable declared inside some block of code enclosed by curly braces is only visible within that block of code, and that variable is not visible outside of that particular block of code.

theWidth 是在 $(window).load 的范围内定义的，而 undefined 超出了 的范围。加载处理程序。

将所有代码包装在 load 处理程序中。

$(window).load(function() {
  var theImage = $('ul li img');
  var theWidth = theImage.width();
  //wrap into mother div
  $('ul').wrap('<div class="gallery-slide" />');
  //assign height width and overflow hidden to gallery-slide
  $('.gallery-slide').css({
    width: function() {
      return theWidth;
    },
    height: function() {
      return theImage.height();
    },
    position: 'relative',
    overflow: 'hidden'
  });
  //get total of image sizes and set as width for ul
  var totalWidth = theImage.length * theWidth;
  $('ul').css({
    width: function() {
      return totalWidth;
    }
  });
  $('ul li img').each(function(intIndex) {
    $(this).nextAll('a').bind("click", function() {

      if ($(this).is(".next")) {
        $(this).parent('li').parent('ul').animate({
          "margin-left": (-(intIndex + 1) * theWidth)
        }, 1000);
      } else if ($(this).is(".previous")) {
        $(this).parent('li').parent('ul').animate({
          "margin-left": (-(intIndex - 1) * theWidth)
        }, 1000);
      } else if ($(this).is(".startover")) {
        $(this).parent('li').parent('ul').animate({
          "margin-left": (0)
        }, 1000);
      }
    });
  });
});