Dynamic default value

README.md

@@ -292,7 +292,7 @@ The library contains several sanitizaters. **Please note, the sanitizers change
 ## Default values
 The most common sanitizer is the `default` property. With it, you can define a default value for all properties. If the property value is `null` or `undefined`, the validator set the defined default value into the property.
 
-**Default value example**:
+**Static Default value example**:
 ```js
 const schema = {
     roles: { type: "array", items: "string", default: ["user"] },
@@ -309,6 +309,27 @@ console.log(obj);
     status: true
 }
 */
+``` 
+**Dynamic Default value**:
+Also you can use dynamic default value by defining a function that returns a value. For example, in the following code, if `createdAt` field not defined in object`, the validator sets the current time into the property:
+
+```js
+const schema = {
+    createdAt: {
+        type: "date",
+        default: () => new Date()
+    }
+};
+
+const obj = {}
+
+v.validate(obj, schema); // Valid
+console.log(obj);
+/*
+{
+    createdAt: Date(2020-07-25T13:17:41.052Z)
+}
+*/
 ```
 
 # Shorthand definitions

lib/validator.js

@@ -93,9 +93,16 @@ class Validator {
 	 * @param {String?} resVar
 	 * @returns {String}
 	 */
-	wrapRequiredCheckSourceCode(rule, innerSrc, resVar) {
+	wrapRequiredCheckSourceCode(rule, innerSrc, context, resVar) {
 		const src = [];
-		const defaultValue = rule.schema.default != null ? JSON.stringify(rule.schema.default) : null;
+		let defaultValue = rule.schema.default != null ? JSON.stringify(rule.schema.default) : null;
+		if (typeof rule.schema.default === "function") {
+			if (!context.customs[rule.index]) context.customs[rule.index] = {};
+			context.customs[rule.index].defaultFn = rule.schema.default;
+
+			defaultValue = `context.customs[${rule.index}].defaultFn()`;
+		}
+
 
 		// Required, optional, forbidden
 		src.push(`
@@ -235,7 +242,7 @@ class Validator {
 					${innerSrc.replace(/%%INDEX%%/g, rule.index)}
 					rule.cycleStack.pop(value);
 				}
-			`, resVar));
+			`, context, resVar));
 
 		} else {
 			this.cache.set(rule.schema, rule);
@@ -250,11 +257,11 @@ class Validator {
 				res.source = res.source.replace(/%%INDEX%%/g, rule.index);
 				const fn = new Function("value", "field", "parent", "errors", "context", res.source);
 				context.fn[rule.index] = fn;
-				sourceCode.push(this.wrapRequiredCheckSourceCode(rule, innerSrc.replace(/%%INDEX%%/g, rule.index), resVar));
+				sourceCode.push(this.wrapRequiredCheckSourceCode(rule, innerSrc.replace(/%%INDEX%%/g, rule.index), context, resVar));
 				sourceCode.push(this.makeCustomValidator({vName: resVar, path: customPath, schema: rule.schema, context, messages: rule.messages, ruleIndex: rule.index}));
 
 			} else {
-				sourceCode.push(this.wrapRequiredCheckSourceCode(rule));
+				sourceCode.push(this.wrapRequiredCheckSourceCode(rule, "", context));
 			}
 		}
 

test/integration.spec.js

@@ -987,22 +987,21 @@ describe("Test strict schema restriction on sub-level", () => {
 describe("Test default value sanitizer", () => {
 	const v = new Validator();
 
-	let schema = {
-		id: { type: "number", default: 5 },
-		name: { type: "string", default: "John" },
-		age: { type: "number", optional: true, default: 33 },
-		roles: { type: "array", items: "string", default: ["user"] },
-		status: { type: "boolean", default: true }
-	};
-	let check = v.compile(schema);
-
-	it("should fill not defined properties", () => {
-		let obj = {
+	it("should fill not defined properties with static value", () => {
+		const schema = {
+			id: { type: "number", default: 5 },
+			name: { type: "string", default: "John" },
+			age: { type: "number", optional: true, default: 33 },
+			roles: { type: "array", items: "string", default: ["user"] },
+			status: { type: "boolean", default: true }
+		};
+		const check = v.compile(schema);
+		const obj = {
 			name: null,
 			status: false
 		};
 
-		let res = check(obj);
+		const res = check(obj);
 
 		expect(res).toBe(true);
 		expect(obj).toEqual({
@@ -1013,5 +1012,23 @@ describe("Test default value sanitizer", () => {
 			status: false
 		});
 	});
+
+	it("should fill not defined properties with dynamic value", () => {
+		let number = { value: 0 };
+		const check = v.compile({
+			a: {
+				type: "number",
+				default: () => number.value++
+			}
+		});
+
+		const o = {};
+
+		expect(check(o)).toBe(true);
+		expect(o.a).toBe(0);
+		delete o.a;
+		check(o);
+		expect(o.a).toBe(1);
+	});
 });