javascript - 在 Javascript 中动态计算溢出量

Question

我有一个容器 div，其设置的高度和宽度相对定位。我想在 Javascript 中计算出它的子项在顶部、右侧、底部和左侧方向超出容器 div 边缘的程度(如果有的话)。任何帮助将不胜感激!

Answer 1

这是top的代码:

var myDivEl = document.getElementById("my-div");
var divTop = myDivEl.getBoundingClientRect().top;

var descendants = myDivEl.getElementsByTagName("*");

var tops = [];
for (var i = 0, descendant; descendant = descendants[i]; ++i) {
   tops.push(descendant.getBoundingClientRect().top);
}

var minTop = Math.min.apply(Math, tops);

var diff = divTop - minTop;

更一般地说:

function getBoundingClientRectDiff(el, propName, minOrMax) {
    var propValue = el.getBoundingClientRect()[propName];

    var descendants = myDivEl.getElementsByTagName("*");

    var descendantPropValues = [];
    for (var i = 0, descendant; descendant = descendants[i]; ++i) {
       descendantPropValues.push(descendant.getBoundingClientRect()[propName]);
    }

    var extremePropValue = Math[minOrMax].apply(Math, descendantPropValues);

    return minOrMax === "Max" ? extremePropValue - propValue
                              : propValue - extremePropValue;
}

function getBoundingClientRectDiffs(el) {
    return {
        top: getBoundingClientRectDiff(el, "top", "Min"),
        right: getBoundingClientRectDiff(el, "right", "Max"),
        bottom: getBoundingClientRectDiff(el, "bottom", "Max"),
        left: getBoundingClientRectDiff(el, "left", "Min")
    };
}

// use like so:
var diffs = getBoundingClientRectDiffs(myDivEl);
console.log(diffs.top, diffs.right, diffs.bottom, diffs.left);