Add basic number and currency formatting

index.js

+// Default Excel value
+const decimalPlaces = 2;
+
 export default function format(v, type='', str=''){
     if(type === '' && str === ''){
         return basicFormat(v);
     }
+
+    // TODO: document possible type values somewhere(if not already)?
+    switch(v.toLowerCase()){
+    case 'number':
+        return numberFormat(v);
+    case 'currency':
+        return currencyFormat(v);
+    }
 }
 
 /**
@@ -22,14 +33,58 @@ export function getHigherBound(){
     return 1e+9;
 };
 
-
+/**
+ * Basic auto-formatting for cases when no formatting is set.
+ * Valid numbers that do not fit into range [abs(lowerBound), abs(higherBound)]
+ * except zeros will be converted to exponential format.
+ * @param {*} x - Input value
+ * @returns {String} String representation of input value
+ */
 export function basicFormat(x){
-    var lowerBound = getLowerBound();
-    var higherBound = getHigherBound();
+    let lowerBound = getLowerBound();
+    let higherBound = getHigherBound();
 
     if(Math.abs(x) >= higherBound || Math.abs(x) < lowerBound && Math.abs(x) !== 0){
         return x.toExponential();
     }
 
-    return '' + x;
+    return x.toString();
 };
+
+/**
+ * Basic number formatting, behaves like Excel number formatting with default
+ * settings (2 decimal places, no 1000 separator)
+ * @param {*} x - Input value
+ * @returns {String} String representation of input value
+ */
+export function numberFormat(x){
+    if(isNaN(x)){
+        throw new Error('Unable to format non-numeric and invalid values!');
+    } else {
+        return parseFloat(x).toLocaleString(
+            undefined, // use OS locale
+            {
+                minimumFractionDigits: decimalPlaces,
+                maximumFractionDigits: decimalPlaces
+            }
+        );
+    }
+}
+
+/**
+ * Basic currency formatting, behaves like Excel currency formatting with default
+ * settings (2 decimal places, russian ruble as a currency suffix)
+ * @param {*} x - Input value
+ * @returns {String} String representation of input value
+ */
+export function currencyFormat(x){
+    if(isNaN(x)){
+        throw new Error('Unable to format non-numeric and invalid values!');
+    } else {
+        return parseFloat(x).toLocaleString(
+            undefined, {
+                style: 'currency', currency: 'RUR' 
+            }
+        );
+    }
+}