js怎么获取光标的位置

const getPosition = function (element) {

let cursorPos = 0;
if (document.selection) {//IE
    var selectRange = document.selection.createRange();
    selectRange.moveStart('character', -element.value.length);
    cursorPos = selectRange.text.length;
} else if (element.selectionStart || element.selectionStart == '0') {
    cursorPos = element.selectionStart;
}
return cursorPos;

}