获取输入框中光标位置

function doGetCaretPosition(oField) {

            // Initialize
            let iCaretPos = 0

            // IE Support
            if (document.selection) {

                // Set focus on the element
                oField.focus()

                // To get cursor position, get empty selection range
                let oSel = document.selection.createRange()

                // Move selection start to 0 position
                oSel.moveStart('character', -oField.value.length)

                // The caret position is selection length
                iCaretPos = oSel.text.length
            }

            // Firefox support
            else if (oField.selectionStart || oField.selectionStart == '0')
                iCaretPos = oField.selectionDirection == 'backward' ? oField.selectionStart : oField.selectionEnd;

            // Return results
            return iCaretPos
        }

##资料 Get cursor position (in characters) within a text Input field