Add js web stuff to landing page + documentation

go/jsruntime/finance.ts

@@ -0,0 +1,98 @@
+// Format a number as USD currency.
+// If `showChangeIfExists` is false, the cents value is only shown if there are leftover cents
+// after converting to dollars (i.e. amount=1000 would be shown as $10, but amount=1001 would be
+// shown as $10.01). If true, cents are always displayed.
+export function formatCurrency(amount: number, showChangeIfExists: boolean = true): string {
+    const dollars = amount / 100;
+    return new Intl.NumberFormat("en-US", {
+        minimumFractionDigits: 2,
+        maximumFractionDigits: 2,
+        trailingZeroDisplay: (showChangeIfExists ? "auto" : "stripIfInteger"),
+        useGrouping: false,
+    }).format(dollars);
+}
+
+// // Same as formatMoney() but with commas.
+export function formatCurrencyWithCommas(amount: number, showChangeIfExists: boolean = true): string {
+    const dollars = amount / 100;
+    return new Intl.NumberFormat("en-US", {
+        minimumFractionDigits: 2,
+        maximumFractionDigits: 2,
+        trailingZeroDisplay: (showChangeIfExists ? "auto" : "stripIfInteger"),
+    }).format(dollars);
+}
+
+// takes a number such as 123456, and outputs (1234, 56) as strings
+export function splitCurrency(amount: number): [string, string] {
+    // Calculate dollars as a string (without cents)
+    const dollars = Math.floor(amount / 100).toString();
+    // Calculate cents as a string with leading zero if necessary;
+    const cents = (amount % 100).toString().padStart(2, "0");
+    return [dollars, cents];
+}
+
+export function moneyToNumber(input: string): number {
+    if (!input.includes(".")) {
+        input += ".00";
+    } else if (input.split(".").length - 1 === 1) {
+        const digits = input.split(".");
+        if (digits[1].length === 1) {
+            input += "0";
+        }
+    }
+    let processed = input
+        .replaceAll(".", "")
+        .replaceAll(",", "")
+        .replaceAll(" ", "");
+    return parseInt(processed);
+}
+
+export function formatRate(rate: number): string {
+    return (rate / 1000).toFixed(3);
+}
+
+export function processDiscount(discount: string): number {
+    const discountFloat = parseFloat(discount);
+
+    if (discountFloat < 0) {
+        return 0;
+    } else if (discountFloat > 100) {
+        return 100;
+    }
+
+    return discountFloat;
+}
+
+// Takes days as an input and outputs the string representation of the number
+// of days, months, or years in the term based on which unit is the best fit
+// for the amount of days along with the corresponding unit string.
+export function daysToRateTerm(days: number): [string, string] {
+    const years = Math.floor(days / 365);
+    const months = Math.floor((days - years*365) / 30);
+    const dayRemainder = days - years*365 - months*30;
+
+    if (days == 0) { // Return empty string for value
+        return ["", "days"];
+    } else if (days <= 270 || dayRemainder > 0) {
+        return [days.toString(), "days"]
+    } else if (months > 0) {
+        return [(months + years*12).toString(), "months"];
+    } else {
+        return [years.toString(), "years"];
+    }
+}
+
+export function rateTermToDays(value: string, unit: string): number {
+    const valueNum = parseInt(value);
+
+    switch (unit) {
+        case "months":
+            const years = Math.floor(valueNum / 12);
+            const months = valueNum % 12;
+            return years*365 + months*30;
+        case "years":
+            return valueNum * 365;
+        default: // case "days":
+            return valueNum;
+    }
+}