flow like the river

BACK_BACK/node_modules/onetime/index.js

@@ -0,0 +1,39 @@
+'use strict';
+const mimicFn = require('mimic-fn');
+
+module.exports = (fn, opts) => {
+	// TODO: Remove this in v3
+	if (opts === true) {
+		throw new TypeError('The second argument is now an options object');
+	}
+
+	if (typeof fn !== 'function') {
+		throw new TypeError('Expected a function');
+	}
+
+	opts = opts || {};
+
+	let ret;
+	let called = false;
+	const fnName = fn.displayName || fn.name || '<anonymous>';
+
+	const onetime = function () {
+		if (called) {
+			if (opts.throw === true) {
+				throw new Error(`Function \`${fnName}\` can only be called once`);
+			}
+
+			return ret;
+		}
+
+		called = true;
+		ret = fn.apply(this, arguments);
+		fn = null;
+
+		return ret;
+	};
+
+	mimicFn(onetime, fn);
+
+	return onetime;
+};