五种数字格式化方法添加逗号，分割

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    <head>
        <meta charset="utf-8" />
        <title>五种数字格式化方法 添加逗号 ， </title>
    </head>
    <body>
        <script type="text/javascript">
            function f1(val) {
                let arrtemp = (val + \'\').split(\'.\');
                let strNew = \'\'

                function cf(val) {
                    let s = \'\',
                        ss = val.split(\'\').reverse().join(\'\');
                    for (let i = 0; i < ss.length; i++) {
                        s += ss[i]
                        if (i % 3 == 2 && i != ss.length - 1) {
                            s += \',\'
                        }
                    }
                    str = s.split(\'\').reverse().join(\'\')
                    return str;
                }
                if (arrtemp.length == 2) {
                    if (arrtemp[0].length > 3) {
                        strNew = cf(arrtemp[0]) + \'.\' + arrtemp[1]
                    } else {
                        strNew = arrtemp[0] + \'.\' + arrtemp[1]
                    }
                } else {
                    if (arrtemp[0].length > 3) {
                        strNew = cf(arrtemp[0])
                    } else {
                        strNew = arrtemp[0]
                    }
                }
                return strNew;
            }



            function f2(val = 0) {
                let nerVal = \'\',
                    valStr = (val + \'\').split(\'.\');

                function cf(val) {
                    let arr = [],
                        cnt = 0;
                    for (let i = val.length - 1; i >= 0; i--) {
                        cnt++;
                        arr.unshift(val[i]);
                        if (cnt % 3 == 0 && i != 0) {
                            arr.unshift(\',\');
                        }
                    }
                    return arr.join(\'\');
                }

                // val 带小数点
                if (valStr.length == 2) {
                    nerVal = cf(valStr[0]) + \'.\' + valStr[1]
                } else {
                    nerVal = cf(valStr[0])
                }
                return nerVal;
            }

            function f3(val = 0) {
                let nerVal = \'\',
                    valStr = (val + \'\').split(\'.\');

                function cf(val) {
                    let s = \'\',
                        cnt = 0;
                    for (let i = val.length - 1; i >= 0; i--) {
                        cnt++;
                        s = val.charAt(i) + s;
                        if (cnt % 3 == 0 && i != 0) {
                            s = \',\' + s;
                        }
                    }
                    return s;
                }

                // val 带小数点
                if (valStr.length == 2) {
                    nerVal = cf(valStr[0]) + \'.\' + valStr[1]
                } else {
                    nerVal = cf(valStr[0])
                }
                return nerVal;
            }

            function f4(val = 0) {
                let nerVal = \'\',
                    valStr = (val + \'\').split(\'.\');

                function cf(val) {
                    let s = \'\',
                        cnt = 0;
                    while (val.length > 3) {
                        s = \',\' + val.slice(-3);
                        val = val.slice(0, val.length - 3)
                    }
                    if (val) {
                        s = val + s;
                    }
                    return s;
                }

                // val 带小数点
                if (valStr.length == 2) {
                    nerVal = cf(valStr[0]) + \'.\' + valStr[1]
                } else {
                    nerVal = cf(valStr[0])
                }
                return nerVal;
            }

            function f5(val = 0) {
                let nerVal = \'\',
                    valStr = (val + \'\').split(\'.\');

                function cf(val) {
                    return val.replace(/(\d)(?=(?:\d{3})+$)/g, \'$1,\');
                }

                // val 带小数点
                if (valStr.length == 2) {
                    nerVal = cf(valStr[0]) + \'.\' + valStr[1]
                } else {
                    nerVal = cf(valStr[0])
                }
                return nerVal;
            }
            console.log(f5(122255.3))
        </script>
    </body>
</html>