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Converts US/Imperial units to SI/Metric on visible text only, rounding metric values to 2 decimals.
// ==UserScript==
// @name Metric Converter
// @namespace https://violentmonkey.github.io/
// @version 1.2
// @description Converts US/Imperial units to SI/Metric on visible text only, rounding metric values to 2 decimals.
// @author Alyssa B. Morton
// @license MIT
// @match *://*/*
// @grant none
// @run-at document-end
// ==/UserScript==
(function() {
'use strict';
// Helper: round to 2 decimal places
function round(n) {
return Math.round(n * 100) / 100;
}
// Conversion functions
const conversions = [
{ regex: /(\d+(?:\.\d+)?)\s?(inch|inches|in)\b/gi, convert: n => `${n} in【${round(n*0.0254)} m】` },
{ regex: /(\d+(?:\.\d+)?)\s?(foot|feet|ft)\b/gi, convert: n => `${n} ft【${round(n*0.3048)} m】` },
{ regex: /(\d+(?:\.\d+)?)\s?(yard|yd)\b/gi, convert: n => `${n} yd【${round(n*0.9144)} m】` },
{ regex: /(\d+(?:\.\d+)?)\s?(mile|mi)\b/gi, convert: n => `${n} mi【${round(n*1.60934)} km】` },
{ regex: /(\d+(?:\.\d+)?)\s?(pound|lbs|lb)\b/gi, convert: n => `${n} lb【${round(n*0.453592)} kg】` },
{ regex: /(\d+(?:\.\d+)?)\s?(ounce|oz)\b/gi, convert: n => `${n} oz【${round(n*0.0283495)} kg】` },
{ regex: /(\d+(?:\.\d+)?)\s?(stone|st)\b/gi, convert: n => `${n} st【${round(n*6.35029)} kg】` },
{ regex: /(\d+(?:\.\d+)?)\s?(gallon|gal)\b/gi, convert: n => `${n} gal【${round(n*3.78541)} L】` },
{ regex: /(\d+(?:\.\d+)?)\s?(quart|qt)\b/gi, convert: n => `${n} qt【${round(n*0.946353)} L】` },
{ regex: /(\d+(?:\.\d+)?)\s?(pint|pt)\b/gi, convert: n => `${n} pt【${round(n*0.473176)} L】` },
{ regex: /(\d+(?:\.\d+)?)\s?(fluid ounce|fl oz)\b/gi, convert: n => `${n} fl oz【${round(n*0.0295735)} L】` },
{ regex: /(\d+(?:\.\d+)?)\s?cup\b/gi, convert: n => `${n} cup【${round(n*0.24)} L】` },
{ regex: /(\d+(?:\.\d+)?)\s?mpg\b/gi, convert: n => `${n} mpg【${round(235.214 / n)} L/100 km】` },
{ regex: /(\d+(?:\.\d+)?)\s?mph\b/gi, convert: n => `${n} mph【${round(n*1.60934)} km/h】` },
{ regex: /(\d+(?:\.\d+)?)\s?°F\b/gi, convert: n => `${n}°F【${round((n-32)*5/9)}°C】` },
// Area
{ regex: /(\d+(?:\.\d+)?)\s?(sq\. ft|ft²)/gi, convert: n => `${n} ${RegExp.$2}【${round(n*0.092903)} m²】` },
{ regex: /(\d+(?:\.\d+)?)\s?(sq\. yd|yd²)/gi, convert: n => `${n} ${RegExp.$2}【${round(n*0.836127)} m²】` },
// Volume
{ regex: /(\d+(?:\.\d+)?)\s?(cu\. ft|ft³)/gi, convert: n => `${n} ${RegExp.$2}【${round(n*0.0283168)} m³】` },
{ regex: /(\d+(?:\.\d+)?)\s?(cu\. in|in³)/gi, convert: n => `${n} ${RegExp.$2}【${round(n*0.0000163871)} m³】` },
];
// Walk through visible text nodes only
function walkVisible(node) {
const walker = document.createTreeWalker(
node,
NodeFilter.SHOW_TEXT,
{
acceptNode: function(n) {
// Ignore empty text, scripts, styles, inputs, textareas, links
if (!n.nodeValue.trim()) return NodeFilter.FILTER_REJECT;
const parent = n.parentNode;
if (!parent) return NodeFilter.FILTER_REJECT;
const ignoredTags = ['SCRIPT','STYLE','TEXTAREA','INPUT','CODE','A'];
if (ignoredTags.includes(parent.tagName)) return NodeFilter.FILTER_REJECT;
return NodeFilter.FILTER_ACCEPT;
}
},
false
);
let n;
while(n = walker.nextNode()) {
handleText(n);
}
}
// Replace text with converted units
function handleText(textNode) {
let text = textNode.nodeValue;
conversions.forEach(item => {
text = text.replace(item.regex, (match, value) => {
const num = parseFloat(value);
if (isNaN(num)) return match;
return item.convert(num);
});
});
textNode.nodeValue = text;
}
// Run on page
walkVisible(document.body);
})();