Vue+ElementUI项目笔记（四、表单+计算）

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count.js计算插件

  /** 小数计算 
  * @example: 
  * 0.1+0.2     //0.30000000000000004 
  * var a=Decimal('0.1');var b=Decimal('0.2'); 
  * a.add(b).toNumber()    //0.3 
  * 四舍五入，保留一位小数 
  * a.add(b).add(0.14).toNumber(1)  //0.4 
  * Decimal.add(0.1,0.2,0.3).toNumber()  //0.6 
  * Decimal.add([0.1,0.2,0.3]).toNumber()  //0.6 
  * (0.1+0.2+0.3)*2/0.5      //2.4000000000000004 
   * Decimal.add([0.1,0.2,0.3]).mul(2).div(0.5).toNumber() //2.4 
    * */

(function (ROOT, factory) {
if (typeof exports === 'object') {
// Node.  
module.exports = factory();
} else if (typeof define === 'function' && define.amd) {
// AMD. Register as an anonymous module.  
define(factory);
} else {
// Browser globals (root is window)  
ROOT.Decimal = factory();
}
 }((0, eval)(this), function () {
  var DECIMAL_SEPARATOR = '.';

  // Decimal  
    var Decimal = function (num) {
if (!this || this.constructor != Decimal) {
  return new Decimal(num);
}

if (num instanceof Decimal) {
  return num;
}

this.internal = String(num);
this.as_int = as_integer(this.internal);

this.add = function (target) {
  var operands = [this, new Decimal(target)];
  operands.sort(function (x, y) {
    return x.as_int.exp - y.as_int.exp
  });

  var smallest = operands[0].as_int.exp;
  var biggest = operands[1].as_int.exp;

  var x = Number(format(operands[1].as_int.value, biggest - smallest));
  var y = Number(operands[0].as_int.value);

  var result = String(x + y);

  return Decimal(format(result, smallest));
};

this.sub = function (target) {
  return Decimal(this.add(target * -1));
};

this.mul = function (target) {
  target = new Decimal(target);
  var result = String(this.as_int.value * target.as_int.value);
  var exp = this.as_int.exp + target.as_int.exp;

  return Decimal(format(result, exp));
};

this.div = function (target) {
  target = new Decimal(target);

  var smallest = Math.min(this.as_int.exp, target.as_int.exp);

  var x = Decimal.mul(Math.pow(10, Math.abs(smallest)), this);
  var y = Decimal.mul(Math.pow(10, Math.abs(smallest)), target);
  return Decimal(x / y);
};

this.toString = function (precision) {
  if (isNumber(precision)) {
    return '' + toFixed(Number(this.internal), precision);
  }
  return this.internal;
};

this.toNumber = function (precision) {
  if (isNumber(precision)) {
    return toFixed(Number(this.internal), precision);
  }
  return Number(this.internal);
}
};

var as_integer = function (number) {
number = String(number);

var value,
  exp,
  tokens = number.split(DECIMAL_SEPARATOR),
  integer = tokens[0],
  fractional = tokens[1];

if (!fractional) {
  var trailing_zeros = integer.match(/0+$/);

  if (trailing_zeros) {
    var length = trailing_zeros[0].length;
    value = integer.substr(0, integer.length - length);
    exp = length;
  } else {
    value = integer;
    exp = 0;
  }
} else {
  value = parseInt(number.split(DECIMAL_SEPARATOR).join(''), 10);
  exp = fractional.length * -1;
}

return {
  'value': value,
  'exp': exp
};
};


 // Helpers  
var neg_exp = function (str, position) {
position = Math.abs(position);

var offset = position - str.length;
var sep = DECIMAL_SEPARATOR;

if (offset >= 0) {
  str = zero(offset) + str;
  sep = '0.';
}

var length = str.length;
var head = str.substr(0, length - position);
var tail = str.substring(length - position, length);
return head + sep + tail;
};

 var pos_exp = function (str, exp) {
var zeros = zero(exp);
return String(str + zeros);
};

 var format = function (num, exp) {
num = String(num);
var func = exp >= 0 ? pos_exp : neg_exp;
return func(num, exp);
 };

 var zero = function (exp) {
return new Array(exp + 1).join('0');
 };

  var methods = ['add', 'mul', 'sub', 'div'];
 for (var i = 0; i < methods.length; i++) {
(function (method) {
  Decimal[method] = function () {
    var args = [].slice.call(arguments);
    if (isArray(args[0])) {
      args = args[0];
    }
    if (args.length == 1) {
      return new Decimal(args[0]);
    }
    var option = args[args.length - 1];

    var sum = new Decimal(args[0]),
      index = 1;
    while (index < args.length) {
      sum = sum[method](args[index]);
      index++;
    }
    return sum;
  };
})(methods[i]);
 }

 var toFixed = function (number, precision) {
var multiplier = Math.pow(10, precision + 1),
  wholeNumber = Math.floor(number * multiplier);
return Math.round(wholeNumber / 10) * 10 / multiplier;
  };
 var isNumber = function (o) {
return Object.prototype.toString.call(o).slice(8, -1) === 'Number';
 };
  var isArray = function (o) {
return Object.prototype.toString.call(o).slice(8, -1) === 'Array';
  };
var isObject = function (o) {
return Object.prototype.toString.call(o).slice(8, -1) === 'Object';
 };
return Decimal;
 }));