只控制input框只能输入数字，并控制小数位数

<input type="text" id="phone" name="phone" class="text"
onkeyup="extractNumber(this, 0, false);"/>

extractNumber(this, 0, false)，中间的参数就是这只小数点后的位数

function extractNumber(obj, decimalPlaces, allowNegative) {

    var temp = obj.value;

    // avoid changing things if already formatted correctly

    var reg0Str = '[0-9]*';

    if (decimalPlaces > 0) {

        reg0Str += '\\.?[0-9]{0,' + decimalPlaces + '}';

    } else if (decimalPlaces < 0) {

        reg0Str += '\\.?[0-9]*';

    }

    reg0Str = allowNegative ? '^-?' + reg0Str : '^' + reg0Str;

    reg0Str = reg0Str + '$';

    var reg0 = new RegExp(reg0Str);

    if (reg0.test(temp)) return true;

    // first replace all non numbers

    var reg1Str = '[^0-9' + (decimalPlaces != 0 ? '.' : '') + (allowNegative ? '-' : '') + ']';

    var reg1 = new RegExp(reg1Str, 'g');

    temp = temp.replace(reg1, '');

    if (allowNegative) {

        // replace extra negative

        var hasNegative = temp.length > 0 && temp.charAt(0) == '-';

        var reg2 = /-/g;

        temp = temp.replace(reg2, '');

        if (hasNegative) temp = '-' + temp;

    }

    if (decimalPlaces != 0) {

        var reg3 = /\./g;

        var reg3Array = reg3.exec(temp);

        if (reg3Array != null) {

            // keep only first occurrence of .

            // and the number of places specified by decimalPlaces or the entire string if decimalPlaces < 0

            var reg3Right = temp.substring(reg3Array.index + reg3Array[0].length);

            reg3Right = reg3Right.replace(reg3, '');

            reg3Right = decimalPlaces > 0 ? reg3Right.substring(0, decimalPlaces) : reg3Right;

            temp = temp.substring(0, reg3Array.index) + '.' + reg3Right;

        }

    }

    obj.value = temp;
}