Automatically converts imperial units to metric units
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// ==UserScript==
// @name Universal metric translator
// @namespace https://bennyjacobs.nl/userscripts/Universal-metric-translator
// @description Automatically converts imperial units to metric units
// @include about:addons
// @include http*
// @include https*
// @version 2.0.2
// @grant none
// ==/UserScript==
// \b\d+(\.\d+)?\s+unit\b
// Flags: global, insensitive
var createTransformationRegEx = function(unit) {
return new RegExp('\\b\\d+(\\.\\d+)?\\s*' + unit + '\\b', "gi");
};
// Sources:
// https://en.wikipedia.org/wiki/Imperial_units
// https://en.wikipedia.org/wiki/Metre
// https://en.wikipedia.org/wiki/Square_metre
// https://en.wikipedia.org/wiki/Litre
var tranformationTable = [
// Temperature
{
from: '(F|fahrenheit|fahrenheits|degrees F|degrees fahrenheit)',
to: '℃',
conversation: function(fahrenheits){
return ((fahrenheits - 32) / 1.8).toFixed(2);
}
},
// Distance
{
from: 'thou',
to: 'µm',
conversation: 25.4,
},
{
from: 'inch(es|e)?',
to: 'mm',
conversation: 25.4,
},
{
from: '(feets?|foot)',
to: 'm',
conversation: 0.3048,
},
{
from: '(yards?|yd)',
to: 'm',
conversation: 0.9144,
},
{
from: 'chains?',
to: 'm',
conversation: 20.1168,
},
{
from: '(furlongs?|fur)',
to: 'm',
conversation: 201.168,
},
{
from: 'miles?',
to: 'km',
conversation: 1.609344,
},
{
from: 'leagues?',
to: 'km',
conversation: 4.828032,
},
// Maritime distances
{
from: '(fathoms?|ftm)',
to: 'm',
conversation: 1.853184,
},
{
from: 'cables?',
to: 'm',
conversation: 185.3184,
},
{
from: 'nautical\\smiles?', // Note: two backslashes as we are escaping a javascript string
to: 'km',
conversation: 1.853184,
},
// Gunter's survey units (17th century onwards)
{
from: 'link',
to: 'm',
conversation: 0.201168,
},
{
from: 'rod',
to: 'm',
conversation: 5.0292,
},
{
from: 'chain',
to: 'm',
conversation: 20.1168,
},
// Area
{
from: 'acres?',
to: 'km²',
conversation: 4.0468564224,
},
// Volume
{
from: '(fluid ounces?|fl oz)',
to: 'ml',
conversation: 28.4130625,
},
{
from: 'gill?',
to: 'ml',
conversation: 142.0653125,
},
{
from: '(pints?|pt)',
to: 'l',
conversation: 0.56826125,
},
{
from: 'quarts?',
to: 'l',
conversation: 1.1365225,
},
{
from: 'gal(lons?)?',
to: 'l',
conversation: 4.54609,
},
//Weight
{
from: 'grains?',
to: 'mg',
conversation: 64.79891,
},
{
from: 'drachm',
to: 'g',
conversation: 1.7718451953125,
},
{
from: '(ounces?|oz)',
to: 'g',
conversation: 28.349523125,
},
// {
// from: 'pounds?', // Pound is ambiguous. It can be a currency. Therefore we don't touch it.
// to: 'g',
// conversation: 453.59,
// },
{
from: 'stones?',
to: 'kg',
conversation: 6.35029318,
},
{
from: 'quarters?',
to: 'kg',
conversation: 12.70058636,
},
{
from: 'hundredweights?',
to: 'kg',
conversation: 50.80234544,
},
// A 'ton' might belong here, but there exist a metric ton and a imperial ton.
];
tranformationTable.forEach(function (transformationRule) {
transformationRule.regex = createTransformationRegEx(transformationRule.from);
});
var replaceSubstring = function(originalText, index, length, replacement) {
var before_substring = originalText.substring(0, index);
var after_substring = originalText.substring(index+length);
return before_substring + replacement + after_substring;
};
function round_number(num, dec) {
return Math.round(num * Math.pow(10, dec)) / Math.pow(10, dec);
}
// The transformText function is idempotent.
// Repeated calls on the output will do nothing. Only the first invocation has any effect.
// The input will be returned on repeated calls.
var transformText = function(text) {
tranformationTable.forEach(function (transformationRule) {
var match = null;
transformationRule.regex.lastIndex = 0;
do
{
match = transformationRule.regex.exec(text);
if(match)
{
var old_value = round_number(parseFloat(match[0]), 2)
var new_value;
if(typeof transformationRule.conversation == 'function')
{
new_value = transformationRule.conversation(old_value);
}
else
{
new_value = old_value * transformationRule.conversation;
}
var new_unit = transformationRule.to;
var new_substring = "" + new_value + " " + new_unit;
text = replaceSubstring(text, match.index, match[0].length, new_substring );
// Move the matching index past whatever we have replaced.
// Note: The replacement can be shorter or longer.
transformationRule.regex.lastIndex = transformationRule.regex.lastIndex + (new_substring.length - match[0].length);
}
} while(match);
});
return text;
};
var handleTextNode = function(textNode) {
var transformedText = transformText(textNode.nodeValue);
if(textNode.nodeValue != transformedText)
textNode.nodeValue = transformedText;
};
// Travel the node(s) in a recursive fashion.
var walk = function(node) {
var child, next;
switch (node.nodeType) {
case 1: // Element
case 9: // Document
case 11: // Document fragment
child = node.firstChild;
while (child) {
next = child.nextSibling;
walk(child);
child = next;
}
break;
case 3: // Text node
handleTextNode(node);
break;
default:
break;
}
};
var MutationObserver = (window.MutationObserver || window.WebKitMutationObserver);
var observer = new MutationObserver(function (mutations) {
mutations.forEach(function (mutation) {
if(mutation.type == 'childList') {
for (var i = 0; i < mutation.addedNodes.length; ++i) {
walk(mutation.addedNodes[i]);
}
} else if (mutation.type == 'characterData') {
handleTextNode(mutation.target);
}
});
});
observer.observe(document, {
childList: true,
characterData: true,
subtree: true,
});
walk(document.body);