Adds the function to an object that returns a parameter value or a default value (in case of parameter is missing in object)

README.md

Adds the function to an object that returns a parameter value or a default value (in case of parameter is missing in object)

Use cases:

• Options backward compatability
• Local and global parameters (global as defaults)
• Getting missing localization strings

Example:

	var obj = {
		param1: "a",
		param2: 10,
		param3: {
			param4: {
				param5: 25
			}
		}
	};
	var defaultObj = {
		param1: "a1",
		param2: 11,
		param3: {
			param4: {
				param5: 25,
				param6: 25
			}
		},
		param7: "b"
	};

	initDefaultParams(obj, defaultObj);

	var param1 = obj.getParamOrDefault('param1'); //param1 = "a"
	var param7 = obj.getParamOrDefault('param7'); //param7 = "b"
	var param345 = obj.getParamOrDefault('param3.param4.param5'); //param345 = 25
	var param346 = obj.getParamOrDefault('param3.param4.param6'); //param346 = 25

default-params.js

/**
 * Initialize default params for object and method to get them
 * @param  {Object} obj           Object with params
 * @param  {Object} defaultParams Default params object
 * @return {Object}               Object with "getParamOrDefault" method
 */
function initDefaultParams(obj, defaultParams) {

	/**
	 * Get parameter from options or from default options (in case of missing parameter)
	 * @param  {String} param Parameter name (e.g. "chart.title.font.size")
	 * @return {Object}       Parameter value
	 */
	var getParamOrDefault = function(param) {

		/**
		 * Get parameter from options natively or return undefined
		 * @param  {Array} params       Array of param names chain ("title.font.size" must be sent as ["title", "font", "size"])
		 * @param  {Object} parentParam Parent parameter value
		 * @return {Object}             Parameter value or undefined in case of parameter missing
		 */
		var getParams = function(params, parentParam) {
			var firstParam = params.shift();
			var firstParamValue = parentParam[firstParam];
			if (firstParamValue != undefined) {
				if (params.length == 0) {
					return firstParamValue;
				} else {
					return getParams(params, firstParamValue);
				}
			} else {
				return undefined;
			}
		};

		var params = param.split('.');
		var paramValue = getParams(params, this);
		if (paramValue == undefined) {
			params = param.split('.');
			paramValue = getParams(params, defaultParams);
		}
		return paramValue;
	};

	obj.getParamOrDefault = getParamOrDefault;
	return obj;
}

default-params.test.js

'use strict';

describe('Default params', function() {
	var obj = {
		param1: "a",
		param2: 10,
		param3: {
			param4: {
				param5: 25
			}
		}
	};
	var defaultObj = {
		param1: "a1",
		param2: 11,
		param3: {
			param4: {
				param5: 25,
				param6: 25
			}
		},
		param7: "b"
	};

	initDefaultParams(obj, defaultObj);

	it("Getting params from object", function() {
		var param1 = obj.getParamOrDefault('param1');
		expect(param1).toBe(obj.param1);
	});

	it("Getting nesting params from object", function() {
		var param345 = obj.getParamOrDefault('param3.param4.param5');
		expect(param345).toBe(obj.param3.param4.param5);
	});

	it("Getting missing params from default object", function() {
		var param7 = obj.getParamOrDefault('param7');
		expect(param7).toBe(defaultObj.param7);
	});

	it("Getting missing nesting params from default object", function() {
		var param346 = obj.getParamOrDefault('param3.param4.param6');
		expect(param346).toBe(defaultObj.param3.param4.param6);
	});
});