Add is.any() and is.all() methods (#19)

index.js

@@ -181,4 +181,31 @@ const isEmptyMapOrSet = x => (is.map(x) || is.set(x)) && x.size === 0;
 
 is.empty = x => !x || isEmptyStringOrArray(x) || isEmptyObject(x) || isEmptyMapOrSet(x);
 
+const predicateOnArray = (method, predicate, values) => {
+	// `values` is the calling function's "arguments object".
+	// We have to do it this way to keep node v4 support.
+	// So here we convert it to an array and slice off the first item.
+	values = Array.prototype.slice.call(values, 1);
+
+	if (is.function(predicate) === false) {
+		throw new TypeError(`Invalid predicate: ${util.inspect(predicate)}`);
+	}
+
+	if (values.length === 0) {
+		throw new TypeError(`Invalid number of values`);
+	}
+
+	return method.call(values, predicate);
+};
+
+// We have to use anonymous functions for the any() and all() methods
+// to get the arguments since we can't use rest parameters in node v4.
+is.any = function (predicate) {
+	return predicateOnArray(Array.prototype.some, predicate, arguments);
+};
+
+is.all = function (predicate) {
+	return predicateOnArray(Array.prototype.every, predicate, arguments);
+};
+
 module.exports = is;