index.js

/**
 * Checks a variable against a list of parameters
 * @param {object[]} configs - a list of objects containing variables to be validated and the rules for validation
 * @param {string} configs[].variableValue - the value of the variable to be checked
 * @param {string} configs[].variableText - the name of the variable to be used in the error return strings.
 * @param {number} configs[].min - the minimum characters the variable should be
 * @param {number} configs[].max - the maximum characters the variable should be
 * @returns {string[]} - array of strings containing errors
 */
validateSize = configs => {
	let errors = [];

	for (let i = 0; i < configs.length; i++) {
		if (configs[i].variableValue.length < configs[i].min) {
			errors.push(
				configs[i].variableText +
					" must be a minimum of " +
					configs[i].min +
					" letters."
			);
		} else if (configs[i].variableValue.length > configs[i].max) {
			errors.push(
				configs[i].variableText +
					" must be a maximum of " +
					configs[i].max +
					" letters."
			);
		}
	}

	return errors;
};

/**
 * Checks a request body against an array of required variables
 * @param {object} body - the express request.body object
 * @param {object[]} variables - the variables that are required in the request
 * @param {string} variables[].variable - the name of the variable to be checked
 * @param {string} variables[].variableText - the name of the variable to be used in the return string.
 * @returns {string[]} - a list of strings containing errors
 */
validateRequest = (body, variables) => {
	let existenceErrors = [];

	for (let i = 0; i < variables.length; i++) {
		if (
			!body.hasOwnProperty(variables[i].variable) ||
			body[variables[i].variable] === ""
		) {
			existenceErrors.push("please enter " + variables[i].variableText);
		}
	}

	return existenceErrors;
};

/**
 * Takes an express request body and a config object and validates it.
 * @param {object} body - an express request.body object
 * @param {object[]} configs - a list of objects containing variables to be validated and the rules for validation
 * @param {string} configs[].variable - the name of the variable to be checked
 * @param {string} configs[].variableText - the name of the variable to be used in the error return strings.
 * @param {number} configs[].min - the minimum characters the variable should be
 * @param {number} configs[].max - the maximum characters the variable should be
 * @returns {string[]} - a list of strings containing errors
 */
validate = (body, configs) => {
	let errors = validateRequest(body, configs);

	if (errors == []) {
		return errors;
	}

	//Assign variableValue only after checking if the body actually has these values.
	for (let i = 0; i < configs.length; i++) {
		configs[i].variableValue = body[configs[i].variable];
	}

	errors = validateSize(configs);

	return errors;
};

module.exports = {
	validate
};