docs(error-handling): add error handling docs (#1)

Author: sudkumar

README.md

@@ -13,6 +13,14 @@ import evalExpr from "eval-num-expr";
 
 const value = evalExpr("100 + 3 * 55 + 73 - 73 * 18%");
 // value = 324.86
+
+// With Invalid Expressions handling
+try {
+  const value = evalExpr("100 + (3 * 55");
+} catch (e) {
+  // Will throw an exception for invalid expressions
+  console.error(e.message)
+}
 ```
 
 You can use basic operations (e.g. +, -, \*, /, %, ^ etc.) in you expressions.
@@ -27,10 +35,22 @@ You can use basic operations (e.g. +, -, \*, /, %, ^ etc.) in you expressions.
 
 ## Api
 
-### evalExpr
+> This package supports TypeScript.
 
-This is the default and only from this package.
+### evalExpr
 
-```js
+This is the default and only export from this package.
+
+```typescript
+/**
+ * Evaluate numeric mathematical expression
+ * @param string expression - The expression to evaluate ("24 + 65 * 3 - 48")
+ * @return number - The evaluated value.
+ *
+ * @throws Will throw an error if the expression in invalid.
+ * 
+ * NOTE: When passing floating points, please handle the digits after decimal point
+ * e.g. 2 - 1.1 leads to 0.8999999999999999 intead of .9
+ */
 evalExpr(expressions: string)
 ```

types/index.d.ts

@@ -3,6 +3,8 @@
  * @param string expression - The expression to evaluate ("24 + 65 * 3 - 48")
  * @return number - The evaluated value.
  *
+ * @throws Will throw an error if the expression in invalid.
+ * 
  * NOTE: When passing floating points, please handle the digits after decimal point
  * e.g. 2 - 1.1 leads to 0.8999999999999999 intead of .9
  */