获取给定一段文字的长度和高度

function getTextWidthAndHeight(str) {
        var span = document.createElement("span");
        span.innerHTML = str;
        span.style.fontSize = "12px";
        span.style.lineHeight = "1em";
        span.style.padding = "0px";
        span.style.margin = "0px";
        document.documentElement.appendChild(span)
        var obj = span.getBoundingClientRect()
        var width = obj.width;
        var height = obj.height;
        span.remove()
        return {
            width,
            height
        }
    }
    
    for (var i = 0; i < 100; i++) {
        console.log(getTextWidthAndHeight(i * 10000 + ""))
    }