1 | <!DOCTYPE html>
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2 | <html>
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3 | <head>
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4 | <title>math.js | currency conversion</title>
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5 |
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6 | <script src="../../dist/math.js"></script>
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7 |
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8 | <style>
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9 | body,
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10 | html,
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11 | input {
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12 | font-size: 11pt;
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13 | font-family: verdana, arial, sans-serif;
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14 | color: #4d4d4d;
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15 | max-width: 600px;
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16 | }
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17 |
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18 | h1 {
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19 | font-size: 120%;
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20 | }
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21 |
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22 | input {
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23 | padding: 5px;
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24 | width: 400px;
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25 | }
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26 | button {
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27 | padding: 5px;
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28 | }
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29 | </style>
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30 | </head>
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31 | <body>
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32 |
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33 | <h1>Currency conversion with math.js</h1>
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34 |
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35 | <p>
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36 | This example demonstrates how you can fetch actual currencies from <a href="https://fixer.io">fixer.io</a> and use them in math.js.
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37 | </p>
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38 |
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39 | <p>
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40 | Create a (free) account at <a href="https://fixer.io">fixer.io</a> and fill in your API access key below:
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41 | </p>
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42 |
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43 | <form id="fetchForm">
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44 | <input type="text" id="apiKey" placeholder="fixer.io API access key..." />
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45 | <button type="submit" id="ok">Fetch currencies</button>
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46 | </form>
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47 |
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48 | <p id="info">
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49 | </p>
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50 | <div id="form" style="display: none;">
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51 | <p>
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52 | <label for="expr">Enter an expression with currencies:</label>
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53 | </p>
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54 | <p>
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55 | <input id="expr" value="5 EUR + 2 * 3 EUR in USD" /><br/>
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56 | </p>
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57 | <p id="result"></p>
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58 | </div>
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59 |
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60 | <script>
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61 | const accessKey = document.getElementById('apiKey')
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62 | const fetchForm = document.getElementById('fetchForm')
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63 |
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64 | fetchForm.onsubmit = function (event) {
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65 | event.preventDefault()
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66 |
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67 | document.getElementById('info').innerHTML = 'Fetching currencies...'
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68 |
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69 | fetchAndImportCurrencies(accessKey.value)
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70 | .then(function (currencies) {
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71 | document.getElementById('expr').oninput = evaluate
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72 | document.getElementById('form').style.display = ''
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73 | document.getElementById('info').innerHTML = 'Available currencies: ' + currencies.join(', ')
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74 |
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75 | evaluate()
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76 | })
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77 | .catch(function (err) {
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78 | console.error(err)
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79 | document.getElementById('info').innerHTML = '<span style="color: red;">' + err.toString() + '</span>'
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80 | })
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81 | }
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82 |
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83 | function fetchAndImportCurrencies (accessKey) {
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84 |
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85 | return fetch('https://data.fixer.io/api/latest?access_key=' + accessKey)
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86 | .then(function (response) {
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87 | return response.json()
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88 | })
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89 | .then(function (data) {
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90 | if (data.success) {
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91 |
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92 | math.createUnit(data.base)
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93 | Object.keys(data.rates)
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94 | .filter(function (currency) {
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95 | return currency !== data.base
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96 | })
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97 | .forEach(function (currency) {
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98 | math.createUnit(currency, math.unit(1 / data.rates[currency], data.base))
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99 | })
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100 |
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101 |
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102 | return Object.keys(data.rates).concat(data.base)
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103 | }
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104 | else {
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105 | throw new Error(data.error.info)
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106 | }
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107 | })
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108 | }
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109 |
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110 | function evaluate () {
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111 | const expr = document.getElementById('expr')
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112 | const result = document.getElementById('result')
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113 |
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114 | try {
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115 | const resultStr = math.format(math.eval(expr.value), {notation: 'fixed', precision: 2})
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116 | result.innerHTML = '<span style="color: dodgerblue;">' + resultStr + '</span>'
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117 | }
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118 | catch (err) {
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119 | result.innerHTML = '<span style="color: red;">' + err.toString() + '</span>'
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120 | }
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121 | }
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122 | </script>
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123 | </body>
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124 | </html> |
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