mathjs
Version:
Math.js is an extensive math library for JavaScript and Node.js. It features a flexible expression parser with support for symbolic computation, comes with a large set of built-in functions and constants, and offers an integrated solution to work with dif
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HTML
<html lang="en">
<head>
<meta charset="utf-8">
<title>math.js | currency conversion</title>
<script src="../../lib/browser/math.js"></script>
<style>
body,
html,
input {
font-size: 11pt;
font-family: verdana, arial, sans-serif;
color: #4d4d4d;
max-width: 600px;
}
h1 {
font-size: 120%;
}
input {
padding: 5px;
width: 400px;
}
button {
padding: 5px;
}
</style>
</head>
<body>
<h1>Currency conversion with math.js</h1>
<p>
This example demonstrates how you can fetch actual currencies from <a href="https://fixer.io">fixer.io</a> and use them in math.js.
</p>
<p>
Create a (free) account at <a href="https://fixer.io">fixer.io</a> and fill in your API access key below:
</p>
<form id="fetchForm">
<input type="text" id="apiKey" placeholder="fixer.io API access key..." />
<button type="submit" id="ok">Fetch currencies</button>
</form>
<p id="info">
</p>
<div id="form" style="display: none;">
<p>
<label for="expr">Enter an expression with currencies:</label>
</p>
<p>
<input id="expr" value="5 EUR + 2 * 3 EUR in USD" /><br/>
</p>
<p id="result"></p>
</div>
<script>
const accessKey = document.getElementById('apiKey')
const fetchForm = document.getElementById('fetchForm')
fetchForm.onsubmit = function (event) {
event.preventDefault()
document.getElementById('info').innerHTML = 'Fetching currencies...'
fetchAndImportCurrencies(accessKey.value)
.then(function (currencies) {
document.getElementById('expr').oninput = evaluate
document.getElementById('form').style.display = ''
document.getElementById('info').innerHTML = 'Available currencies: ' + currencies.join(', ')
evaluate()
})
.catch(function (err) {
console.error(err)
document.getElementById('info').innerHTML = '<span style="color: red;">' + err.toString() + '</span>'
})
}
function fetchAndImportCurrencies (accessKey) {
// fetch actual currency conversion rates
return fetch('http://data.fixer.io/api/latest?access_key=' + accessKey)
.then(function (response) {
return response.json()
})
.then(function (data) {
if (data.success) {
// import the currencies
math.createUnit(data.base)
Object.keys(data.rates)
.filter(function (currency) {
return currency !== data.base
})
.forEach(function (currency) {
math.createUnit(currency, math.unit(1 / data.rates[currency], data.base))
})
// return an array with all available currencies
return Object.keys(data.rates).concat(data.base)
}
else {
throw new Error(data.error.info)
}
})
}
function evaluate () {
const expr = document.getElementById('expr')
const result = document.getElementById('result')
try {
const resultStr = math.format(math.evaluate(expr.value), {notation: 'fixed', precision: 2})
result.innerHTML = '<span style="color: dodgerblue;">' + resultStr + '</span>'
}
catch (err) {
result.innerHTML = '<span style="color: red;">' + err.toString() + '</span>'
}
}
</script>
</body>
</html>