amazon-converter.js

// ==UserScript==
// @name         AMAZON currency converter
// @namespace    http://tampermonkey.net/
// @version      0.1
// @description  try to take over the world!
// @author       You
// @match        https://www.amazon.com/*
// @match        https://www.amazon.co.uk/*
// @grant        none
// @require      http://code.jquery.com/jquery-latest.js
// ==/UserScript==

$(function() {
    'use strict';
    let host = window.location.host;
    let base;
    var formatter = new Intl.NumberFormat('en-US', {
        style: 'currency',
        currency: 'PHP',
        minimumFractionDigits: 2,
    });
    if(host === 'www.amazon.co.uk'){
        base = 'GBP';
    }else{
        base = 'USD';
    }
    getRate(base);


    function getRate(base){
        function fetchRate(){
            fetch(`//api.fixer.io/latest?base=${base}&symbols=PHP`).then(function(response){
              response.json().then(res=>{
                 let amazon = {};
                 amazon[base] = {
                     date: (new Date()).toDateString(),
                     rate: res.rates.PHP
                 };
                  localStorage.setItem('AMAZON', JSON.stringify(amazon));
                  convertPrices(res.rates.PHP, base);
              });
            });
        }

        var rate = JSON.parse(localStorage.getItem('AMAZON')) || {};
        if(!rate[base]) {
            fetchRate();
        }else{
            if(rate[base].date === (new Date()).toDateString()){
                convertPrices(rate[base].rate, base);
            }else{
                fetchRate();
            }
        }

    }


    function convertPrices(rate, base){
        let prices;
        switch(base){
            case 'GBP':
                prices = $('.a-color-price');
                break;
            default:
                prices = $('.a-link-normal .a-color-base, .a-color-price');
                break;
        }
    prices.each(function(){

        switch(base){
            case 'GBP':
                let price = parseFloat(this.innerText.trim().substr(1)) * rate;
                $(this).text(formatter.format(price));
                break;
            default:
                if($(this).attr('aria-label')){
                    let price = parseFloat($(this).attr('aria-label').substr(1)) * rate;
                    $(this).text(formatter.format(price));
                }else{
                    let price = parseFloat(this.innerText.trim().substr(1)) * rate;
                    if(price) $(this).text(formatter.format(price));
                }
                break;
        }
    });
    }
});