JavaScript 变量不起作用。为什么？

Question

我不了解 javascript 中的变量。我试图在 localScroll 函数发生之前，或更优选地在调整窗口大小时更改/计算“偏移量”(使用变量“theOffset”)。下面的实例都不起作用，接受“//初始​​化偏移量”。

如何更改“$.localScroll”内的变量“theOffset”？

jQuery(function( $ ){

    //initialize offset
    var windowWidth = $(window).width();
    if (windowWidth < 900) {
        theOffset = 0;
    } else {
        theOffset = ($(window).width() - 900) / -2;
    }

$(window).resize(function() {
    //calculate offset
    var windowWidth = $(window).width();
    if (windowWidth < 900) {
        theOffset = 0;
    } else {
        theOffset = ($(window).width() - 900) / -2;
    }
});


    $.localScroll({
        target: '#content',
        queue:true,
        duration:1500,
        hash:true,
        stop:true,
        onBefore:function( e, anchor, $target ){
            //calculate offset
            var windowWidth = $(window).width();
            if (windowWidth < 900) {
                theOffset = 0;
            } else {
                theOffset = ($(window).width() - 900) / -2;
            }
        },
        offset: {top:0, left: theOffset,
        onAfter:function( anchor, settings ){
            if (windowWidth < 900) {
                theOffset = 0;
            } else {
                theOffset = ($(window).width() - 900) / -2;
            }
        }   
    });
});

如果需要知道，我将一个 div 容器置于窗口的中心，并在一个精美的侧滚动网站中进行偏移；)

Answer 1

您可以声明一个 myOffset 对象，该对象将通过对 offset 的引用进行传递:您还可以将几乎四倍的函数细化为单个命名函数:

var myOffset = {top: 0, left: theOffset};
function calcOffset() {
  var windowWidth = $(window).width();
  if (windowWidth < 900) {
    myOffset.left = 0;
  } else {
    myOffset.left = (windowWidth - 900) / -2;
  }
}
calcOffset();
// note leaving off the () will pass the function as a parameter instead of calling it
$(window).resize(calcOffset);

$.localScroll({
    target: '#content',
    queue: true,
    duration: 1500,
    hash: true,
    stop: true,
    onBefore: calcOffset,
    offset: myOffset,
    onAfter: calcOffset
});