银行卡号空格

$(function() {
    $('#kahao').on('keyup', function(e) {
        //只对输入数字时进行处理
        if ((e.which >= 48 && e.which <= 57) ||
            (e.which >= 96 && e.which <= 105)) {
            //获取当前光标的位置
            var caret = this.selectionStart
            //获取当前的value
            var value = this.value
            //从左边沿到坐标之间的空格数
            var sp = (value.slice(0, caret).match(/\s/g) || []).length
            //去掉所有空格
            var nospace = value.replace(/\s/g, '')
            //重新插入空格
            var curVal = this.value = nospace.replace(/(\d{4})/g, "$1 ").trim()
            //从左边沿到原坐标之间的空格数
            var curSp = (curVal.slice(0, caret).match(/\s/g) || []).length
            //修正光标位置
            this.selectionEnd = this.selectionStart = caret + curSp - sp

        }
    })
})