feat($filter): Display Infinity symbol when number is Infinity

Infinity is a value and should not be treated as an empty string

Closes #10421

src/ng/filter/filters.js

@@ -82,6 +82,8 @@ function currencyFilter($locale) {
  *
  * If the input is not a number an empty string is returned.
  *
+ * If the input is an infinite (Infinity/-Infinity) the Infinity symbol '∞' is returned.
+ *
  * @param {number|string} number Number to format.
  * @param {(number|string)=} fractionSize Number of decimal places to round the number to.
  * If this is not provided then the fraction size is computed from the current locale's number
@@ -138,16 +140,22 @@ function numberFilter($locale) {
 
 var DECIMAL_SEP = '.';
 function formatNumber(number, pattern, groupSep, decimalSep, fractionSize) {
-  if (!isFinite(number) || isObject(number)) return '';
+  if (isObject(number)) return '';
 
   var isNegative = number < 0;
   number = Math.abs(number);
+
+  var isInfinity = number === Infinity;
+  if (!isInfinity && !isFinite(number)) return '';
+
   var numStr = number + '',
       formatedText = '',
+      hasExponent = false,
       parts = [];
 
-  var hasExponent = false;
-  if (numStr.indexOf('e') !== -1) {
+  if (isInfinity) formatedText = '\u221e';
+
+  if (!isInfinity && numStr.indexOf('e') !== -1) {
     var match = numStr.match(/([\d\.]+)e(-?)(\d+)/);
     if (match && match[2] == '-' && match[3] > fractionSize + 1) {
       number = 0;
@@ -157,7 +165,7 @@ function formatNumber(number, pattern, groupSep, decimalSep, fractionSize) {
     }
   }
 
-  if (!hasExponent) {
+  if (!isInfinity && !hasExponent) {
     var fractionLen = (numStr.split(DECIMAL_SEP)[1] || '').length;
 
     // determine fractionSize if it is not specified

test/ng/filter/filtersSpec.js

@@ -150,10 +150,10 @@ describe('filters', function() {
       expect(number(Number.NaN)).toEqual('');
       expect(number({})).toEqual('');
       expect(number([])).toEqual('');
-      expect(number(+Infinity)).toEqual('');
-      expect(number(-Infinity)).toEqual('');
+      expect(number(+Infinity)).toEqual('∞');
+      expect(number(-Infinity)).toEqual('-∞');
       expect(number("1234.5678")).toEqual('1,234.568');
-      expect(number(1 / 0)).toEqual("");
+      expect(number(1 / 0)).toEqual('∞');
       expect(number(1,        2)).toEqual("1.00");
       expect(number(.1,       2)).toEqual("0.10");
       expect(number(.01,      2)).toEqual("0.01");