计量单位转换库 [英] Unit of Measure Conversion Library

问题描述

根据用户首选的度量单位设置，抽象出客户端度量单位转换的最佳/最优雅方法是什么？

What is the best/most elegant way to abstract out the conversion of units of measures in the client, based on a user-preferred unit of measure setting?

例如，假设用户A的首选度量单位是metric，而用户B的首选项是imperial。

For example, let's say user A's preferred unit of measure is "metric", while user's B's preference is "imperial".

现在我可以说我计算了以米为单位的东西。当我去显示值时，我需要为每个用户使用不同的转换因子（例如，1米= 1.09361码）。或者说我用 mL 计算了液量。用户B的视图将使用转换236.588237 mL = 1 US cup进行计算。

Now lets say I've calculated the area of something in meters squared. When I go to display the value I need to use different conversion factors for each user (eg, "1 meter = 1.09361 yards"). Or say I've calculated the fluid volume in mL. User B's view will get calculated using the conversion "236.588237 mL = 1 US cup".

是否存在此处任何人都知道的现有javascript库处理这些简单的UOM转换？

Is there an existing javascript library that anyone here knows about that handles these trivial UOM conversions?

推荐答案

这是一个小小的脚本，我只是为了它而扔在一起。它处理克，字节，米和升的所有SI转换，并且我还添加了盎司和磅作为非SI单位的示例。要添加更多内容，您需要：

Here's a little script I threw together just for the heck of it. It handles all the SI conversions for grams, bytes, meters and liters, and also I've added ounces and pounds as an example of non-SI units. To add more, you'll need to:

1. 将基本类型添加到SI或
   
2. 为不遵循SI的项目添加转换率

用法：

$u(1, 'g').as('kg').val(); // converts one gram to kg

您可以使用字符串.val（）获取值表示使用.toString（）或完整的详细信息通过.debug（）

You can get the value out with .val(), a string representation using .toString() or the full details via .debug()

(function () {
    var table = {};

    window.unitConverter = function (value, unit) {
        this.value = value;
        if (unit) {
            this.currentUnit = unit;
        }
    };
    unitConverter.prototype.as = function (targetUnit) {
        this.targetUnit = targetUnit;
        return this;
    };
    unitConverter.prototype.is = function (currentUnit) {
        this.currentUnit = currentUnit;
        return this;
    };

    unitConverter.prototype.val = function () {
        // first, convert from the current value to the base unit
        var target = table[this.targetUnit];
        var current = table[this.currentUnit];
        if (target.base != current.base) {
            throw new Error('Incompatible units; cannot convert from "' + this.currentUnit + '" to "' + this.targetUnit + '"');
        }

        return this.value * (current.multiplier / target.multiplier);
    };
    unitConverter.prototype.toString = function () {
        return this.val() + ' ' + this.targetUnit;
    };
    unitConverter.prototype.debug = function () {
        return this.value + ' ' + this.currentUnit + ' is ' + this.val() + ' ' + this.targetUnit;
    };
    unitConverter.addUnit = function (baseUnit, actualUnit, multiplier) {
        table[actualUnit] = { base: baseUnit, actual: actualUnit, multiplier: multiplier };
    };

    var prefixes = ['Y', 'Z', 'E', 'P', 'T', 'G', 'M', 'k', 'h', 'da', '', 'd', 'c', 'm', 'u', 'n', 'p', 'f', 'a', 'z', 'y'];
    var factors = [24, 21, 18, 15, 12, 9, 6, 3, 2, 1, 0, -1, -2, -3, -6, -9, -12, -15, -18, -21, -24];
    // SI units only, that follow the mg/kg/dg/cg type of format
    var units = ['g', 'b', 'l', 'm'];

    for (var j = 0; j < units.length; j++) {
        var base = units[j];
        for (var i = 0; i < prefixes.length; i++) {
            unitConverter.addUnit(base, prefixes[i] + base, Math.pow(10, factors[i]));
        }
    }

    // we use the SI gram unit as the base; this allows
    // us to convert between SI and English units
    unitConverter.addUnit('g', 'ounce', 28.3495231);
    unitConverter.addUnit('g', 'oz', 28.3495231);
    unitConverter.addUnit('g', 'pound', 453.59237);
    unitConverter.addUnit('g', 'lb', 453.59237);


    window.$u = function (value, unit) {
        var u = new window.unitConverter(value, unit);
        return u;
    };
})();

console.log($u(1, 'g').as('kg').debug());  
console.log($u(1, 'kg').as('g').debug());
console.log($u(1, 'g').as('mg').debug());
console.log($u(1, 'mg').as('g').debug());
console.log($u(1, 'mg').as('kg').debug());

console.log($u(1, 'g').as('oz').debug());
console.log($u(1, 'g').as('lb').debug());

console.log($u(1, 'oz').as('lb').debug());

console.log($u(1, 'lb').as('g').debug());

// this last one throws an exception since you can't convert liters to mg
console.log($u(1, 'l').as('mg').debug());

我把这个转移到了Github上的一个小型仓库，所以如果有人想要改进/增强他们可以这样做：
https://github.com/jerodvenemafm/jsunitconverter

I've moved this to a small repo on Github so if anyone wants to improve/enhance they can do so: https://github.com/jerodvenemafm/jsunitconverter

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