使用Javascript：货币换算([removed] Currency converter)

林在JavaScript中新，我试图做一个简单的汇率换算，它工作正常，当我选择“£英镑”，“£磅”或“£英镑”，“R $真”，但是当我选择“R $雷亚尔” “R $真正的”运行“英镑”，“R $真”计算。

我花了几个小时试图弄清楚这一点（很无奈）。

如何解决呢？ 是否有另一种方式做到这一点？ （也使用“如果”和“否则，如果”同样的问题，试过）。 谢谢！

Here`s的HTML：

<label>Amount:</label>
<input type="text" id="amount" />
<label>From:</label>
<select id="select1">
    <option value="pound">&pound; Pound</option>
    <option value="real">R$ Real</option>
</select>
<label>To:</label>
<select id="select2">
    <option value="pound">&pound; Pound</option>
    <option value="real">R$ Real</option>
</select>
<input type="button" onClick="calculation()" value="calculate" />
<div id="result"></div>

Here`s的JS：

function calculation() {
var amount = document.getElementById('amount').value;
var currency1 = document.getElementById('select1').value;
var currency2 = document.getElementById('select2').value;

switch((currency1)&&(currency2)){
    case "pound":
    case "pound":
        var y = amount * 1;
        document.getElementById('result').innerHTML = "£ " + parseFloat(Math.round(y * 100) / 100).toFixed(2);
        break
    case "pound":
    case "real":
        var x = currency2 = 3.40;
        var y = amount * x;
        document.getElementById('result').innerHTML = "R$ " + parseFloat(Math.round(y * 100) / 100).toFixed(2);
        break
    case "real":
    case "real":
        var y = amount * 1;
        document.getElementById('result').innerHTML = "R$ " + parseFloat(Math.round(y * 100) / 100).toFixed(2);
        break
    case "real":
    case "pound":
        var x = currency2 = 3.40;
        var y = amount / x;
        document.getElementById('result').innerHTML = "£ " + parseFloat(Math.round(y * 100) / 100).toFixed(2);
}}

Answer 1:

要解决您的JS做到以下几点：

问题是，你的交换机会计算到一个字符串，使用的是落空switch语句， 的jsfiddle证明了我的意思 。

JavaScript的开关语句文档

function calculation() {
    var amount = document.getElementById('amount').value;
    var currency1 = document.getElementById('select1').value;
    var currency2 = document.getElementById('select2').value;

    switch (currency1 + ' ' + currency2) {
        case "pound pound":
            var y = amount * 1;
            document.getElementById('result').innerHTML = "£ " + parseFloat(Math.round(y * 100) / 100).toFixed(2);
            break
        case "pound real":
            var x = currency2 = 3.40;
            var y = amount * x;
            document.getElementById('result').innerHTML = "R$ " + parseFloat(Math.round(y * 100) / 100).toFixed(2);
            break
        case "real real":
            var y = amount * 1;
            document.getElementById('result').innerHTML = "R$ " + parseFloat(Math.round(y * 100) / 100).toFixed(2);
            break
        case "real pound":
            var x = currency2 = 3.40;
            var y = amount / x;
            document.getElementById('result').innerHTML = "£ " + parseFloat(Math.round(y * 100) / 100).toFixed(2);
    }
}

使用下面显示的号码，然后干脆把符号在前面，因为这样的代码将在正确的位置，包括负面添加逗号和分隔符。

格式数量的货币：

function formatCurrency(num, precision) {
    //identify '(123)' as a negative number
    if (typeof num == 'string' && num.toString().indexOf('\\(') >= 0) {
        num = '-' + num;
    }

    if (num === '' || (num === '-' && precision === -1)) {
        return;
    }

    // if the number is valid use it, otherwise clean it
    if (isNaN(num)) {
        // clean number
        if (num === '' || (num === '-' && precision === -1)) {
            return;
        }

        if (isNaN(num)) {
            num = '0';
        }
    }

    // evalutate number input
    var numParts = String(num).split('.');
    var isPositive = (num == Math.abs(num));
    var hasDecimals = (numParts.length > 1);
    var decimals = (hasDecimals ? numParts[1].toString() : '0');
    var originalDecimals = decimals;

    // format number
    num = Math.abs(numParts[0]);
    num = isNaN(num) ? 0 : num;
    if (precision >= 0) {
        decimals = parseFloat('1.' + decimals); // prepend "0."; (IE does NOT round 0.50.toFixed(0) up, but (1+0.50).toFixed(0)-1
        decimals = decimals.toFixed(precision); // round
        if (decimals.substring(0, 1) == '2') {
            num = Number(num) + 1;
        }
        decimals = decimals.substring(2); // remove "0."
    }
    num = String(num);

    for (var i = 0; i < Math.floor((num.length - (1 + i)) / 3) ; i++) {
        num = num.substring(0, num.length - (4 * i + 3)) + ',' + num.substring(num.length - (4 * i + 3));
    }

    if ((hasDecimals && precision == -1) || precision > 0) {
        num += '.' + decimals;
    }

    // format symbol/negative
    var format = isPositive ? '%s%n' : '(%s%n)';
    var money = format.replace(/%s/g, '$');
    money = money.replace(/%n/g, num);
    return money;
}

文章来源: Javascript: Currency converter