add addProps and setProps for adding/setting properties of an object,…

… respectively

addProps.js

@@ -0,0 +1,12 @@
+var each = require('./each')
+var copy = require('./copy')
+
+module.exports = function addProps(target, addPropsIfNotExist) {
+	var result = copy(target)
+	each(addPropsIfNotExist, function(val, key) {
+		if (result[key] == undefined) {
+			result[key] = addPropsIfNotExist[key]
+		}
+	})
+	return result
+}

setProps.js

@@ -0,0 +1,10 @@
+var each = require('./each')
+var copy = require('./copy')
+
+module.exports = function setProps(target, overwriteProps) {
+	var result = copy(target)
+	each(overwriteProps, function(val, key) {
+		result[key] = overwriteProps[key]
+	})
+	return result
+}