feat: add support for maxDecimalPlaces on IsNumber (#381)

Author: Jasper Blues

package-lock.json

@@ -1,7 +1,8 @@
 /**
- * Options to be passed to IsURL decorator.
+ * Options to be passed to IsNumber decorator.
  */
 export interface IsNumberOptions {
     allowNaN?: boolean;
     allowInfinity?: boolean;
-}
+    maxDecimalPlaces?: number;
+}

src/validation/ValidationTypeOptions.ts

@@ -150,7 +150,7 @@ export class ValidationTypes {
             case this.IS_DATE:
                 return eachPrefix + "$property must be a Date instance";
             case this.IS_NUMBER:
-                return eachPrefix + "$property must be a number";
+                return eachPrefix + "$property must be a number conforming to the specified constraints";
             case this.IS_INT:
                 return eachPrefix + "$property must be an integer number";
             case this.IS_STRING:

src/validation/ValidationTypes.ts

@@ -435,6 +435,16 @@ export class Validator {
             return options.allowNaN;
         }
 
+        if (options.maxDecimalPlaces) {
+            let decimalPlaces = 0;
+            if ((value % 1) !== 0) {
+                decimalPlaces = value.toString().split(".")[1].length;
+            }
+            if (decimalPlaces > options.maxDecimalPlaces) {
+                return false;
+            }
+        }
+        
         return Number.isFinite(value);
     }
 

src/validation/Validator.ts

@@ -568,6 +568,11 @@ describe("IsNumber", function() {
         someProperty: number;
     }
 
+    class MaxDecimalPlacesTest {
+        @IsNumber({ maxDecimalPlaces: 3 })
+        someProperty: number;
+    }
+
     it("should fail if NaN passed without allowing NaN values", function (done) {
         checkInvalidValues(new MyClass(), [NaN], done);
     });
@@ -602,10 +607,18 @@ describe("IsNumber", function() {
 
     it("should return error object with proper data", function(done) {
         const validationType = "isNumber";
-        const message = "someProperty must be a number";
+        const message = "someProperty must be a number conforming to the specified constraints";
         checkReturnedError(new MyClass(), invalidValues, validationType, message, done);
     });
 
+    it("should pass if number of decimal places within maxDecimalPlaces", function(done) {
+        checkValidValues(new MaxDecimalPlacesTest(), [1.123], done);
+    });
+
+    it("should fail if number of decimal places exceeds maxDecimalPlaces", function(done) {
+        checkInvalidValues(new MaxDecimalPlacesTest(), [1.1234], done);
+    });
+
 });
 
 describe("IsInt", function() {