Merge pull request #1049 from lightninglabs/less-than-cent

Display less than a cent fiat amounts

Author: tanx

src/helper.js

@@ -30,7 +30,14 @@ export const formatFiat = (val, currency) => {
     num = 0;
   }
   const options = { style: 'currency', currency };
-  return new Intl.NumberFormat(undefined, options).format(num);
+  const intl = new Intl.NumberFormat(undefined, options);
+  const str = intl.format(num);
+  if (num < 1 && num > 0 && /0[,.]0{2}/.test(str)) {
+    return `< ${intl.format(0.01)}`;
+  } else if (Math.abs(num) < 1 && Math.abs(num) > 0 && /0[,.]0{2}/.test(str)) {
+    return `< ${intl.format(-0.01)}`;
+  }
+  return str;
 };
 
 /**

test/unit/helper.spec.js

@@ -60,6 +60,48 @@ describe('Helpers Unit Tests', () => {
       expect(num, 'to match', /1[,.]0{3}[,.]0{3}[,.]0{2}/);
       expect(num, 'to match', /\${1}/);
     });
+
+    it('should display one cent', () => {
+      const num = helpers.formatFiat(0.01, 'usd');
+      expect(num, 'to match', /0[,.]0{1}1{1}/);
+      expect(num, 'to match', /\${1}/);
+      expect(num, 'not to match', /^< /);
+    });
+
+    it('should round up to one cent', () => {
+      const num = helpers.formatFiat(0.005, 'usd');
+      expect(num, 'to match', /0[,.]0{1}1{1}/);
+      expect(num, 'to match', /\${1}/);
+      expect(num, 'not to match', /^< /);
+    });
+
+    it('should display less than a cent', () => {
+      const num = helpers.formatFiat(0.004, 'usd');
+      expect(num, 'to match', /0[,.]0{1}1{1}/);
+      expect(num, 'to match', /\${1}/);
+      expect(num, 'to match', /^< /);
+    });
+
+    it('should display less than a cent for small numbers', () => {
+      const num = helpers.formatFiat(0.0000001, 'usd');
+      expect(num, 'to match', /0[,.]0{1}1{1}/);
+      expect(num, 'to match', /\${1}/);
+      expect(num, 'to match', /^< /);
+    });
+
+    it('should display less than a cent for negative small numbers', () => {
+      const num = helpers.formatFiat(0.999999 - 1, 'usd');
+      expect(num, 'to match', /0[,.]0{1}1{1}/);
+      expect(num, 'to match', /\${1}/);
+      expect(num, 'to match', /^< -/);
+    });
+
+    it('should display 0.00 without less than', () => {
+      const num = helpers.formatFiat(0.0, 'usd');
+      expect(num, 'to match', /0[,.]0{2}/);
+      expect(num, 'to match', /\${1}/);
+      expect(num, 'not to match', /^< /);
+    });
   });
 
   describe('parseDate()', () => {