Basic JavaScript Asserts for Type-Checking

asserts.js

/**
* assert - Logs or throws an Error if `boolean` is false,
*  If `boolean` is `true`, nothing happens.
*  If `errorType` is set, throws a new Error of type `errorType` instead of logging to console.
* @param  {Boolean} boolean         The activation Boolean.
* @param  {String} message          The message to log, or include in the Error.
* @param  {Error} errorType = null  If not `null`, throws a new error of `errorType`.
*/
function assert(boolean, message, errorType = null) {
	if (boolean) return;
	if (errorType !== null && (errorType === Error || Error.isPrototypeOf(errorType))) {
		throw new errorType(message);
	} else {
		console.error(message);
	}
}
// Thunks to `assert` for method argument type checking.
assert.props = function (input, props, argName) {
	for (var prop of props[Symbol.iterator]()) {
		assert(prop in input, "Argument " + argName + " must have a \"" + prop + "\" property.", TypeError);
	}
};
assert.argType = (boolean, typeString, argName) =>
	assert(boolean, "Argument " + argName + " must be " + typeString, TypeError);
assert.string = (input, argName) =>
	assert.argType(typeof input === "string", "a String", argName);
assert.number = (input, argName) =>
	assert.argType(typeof input === "number", "a Number", argName);
assert.boolean = (input, argName) =>
	assert.argType(typeof input === "boolean", "a Boolean", argName);
assert.function = (input, argName) =>
	assert.argType(typeof input === "function", "a Function", argName);
assert.object = (input, argName) =>
	assert.argType(typeof (input) === "object", "an Object", argName);
assert.array = (input, argName) =>
	assert.argType(Array.isArray(input), "an Array", argName);
assert.container = (input, argName) =>
	assert.argType(input !== null && (Array.isArray(input) || typeof input === "object"), "an Object or Array", argName);