Fix Issue mathiasbynens#17: "remove differences between `jsesc(data, …

…{ json: true })` and `JSON.stringify(data)"

jsesc.js

@@ -58,6 +58,9 @@
 		return typeof value == 'string' ||
 			toString.call(value) == '[object String]';
 	};
+	var isFunction = function(value) {
+		return typeof value == 'function';
+	};
 
 	/*--------------------------------------------------------------------------*/
 
@@ -108,6 +111,11 @@
 		var result;
 		var isEmpty = true;
 
+		// convert argument to toJSON if needed.
+		if (json && argument && isObject(argument) && isFunction(argument.toJSON)) {
+			argument = argument.toJSON();
+		}
+
 		if (!isString(argument)) {
 			if (isArray(argument)) {
 				result = [];

src/jsesc.js

@@ -58,6 +58,9 @@
 		return typeof value == 'string' ||
 			toString.call(value) == '[object String]';
 	};
+	var isFunction = function(value) {
+		return typeof value == 'function';
+	};
 
 	/*--------------------------------------------------------------------------*/
 
@@ -108,6 +111,11 @@
 		var result;
 		var isEmpty = true;
 
+		// convert argument to toJSON if needed.
+		if (json && argument && isObject(argument) && isFunction(argument.toJSON)) {
+			argument = argument.toJSON();
+		}
+
 		if (!isString(argument)) {
 			if (isArray(argument)) {
 				result = [];

tests/tests.js

@@ -263,6 +263,17 @@
 			'"foo\\u{1D306}bar\\u00A9baz"',
 			'Escaping as JSON with `es6: true`'
 		);
+		equal(
+			jsesc('foo - \uD83D\uDCA9 - foo', {json: true}),
+			'"foo - \\uD83D\\uDCA9 - foo"',
+			'Escaping as JSON is same as JSON.stringify'
+		);
+		var objWithToJson = {'shouldnt be here': 10, toJSON: function() { return {'hello': 'world', 'cat': 'dog', 'pileof': '\uD83D\uDCA9'}; }};
+		equal(
+			jsesc(objWithToJson, {json: true}),
+			'{"hello":"world","cat":"dog","pileof":"\\uD83D\\uDCA9"}',
+			'Escaping obj with toJSON, as JSON, is same as JSON.stringify'
+		);
 	});
 
 	if (runExtendedTests) {