Simple function to build a URL with URI parameters. Function allows for default values and a mechanism to require parameters.

buildURL.ts

/**
 * Simple object that requires each keyed value to be a string.
 */
interface StringObject {[key: string]: string;}

/**
 * Utility function to create a URL with parameters.
 * @param url Base URL to build for.
 * @param uri_values URI parameters to encode add to URL
 * @param default_values Default URI parameters to encode into URL.  Use this to define defaults to add.
 * @param required_keys String array of all the parameter keys that are required.
 * @returns Final URL combining URL and URI
 * 
 * Example:
 * ```typescript
 * var url = _buildURL(
 *   "https://www.google.com",                   // Set Base URL
 *   {"q": "Who is best Pony?"},                 // Set Supplied Search Value
 *   {"q": "What is this TypeScript stuff?"},    // Set Default Search Value
 *   ["q"]                                       // Set Required parameters
 * );
 * ```
 */
function _buildURL(url:string, uri_values: StringObject = {}, default_values: StringObject = {}, required_keys: Array<string> = []) {
    // Merge Default Values with supplied values
    const merged_uri = {...default_values, ...uri_values};

    // Check to ensure all required keys are set
    const hasAllKeys = required_keys.every(key => {
        const has_key = merged_uri.hasOwnProperty(key);
        if (!has_key) throw `${_buildURL.name}}: Required key "${key}" was not set.`;
        return has_key;
    });

    // Build URI and return final URL
    const uri = new URLSearchParams(merged_uri).toString();
    if (uri === "") return url;
    return url + "?" + uri;
}