diff --git a/src/dataToEsm.ts b/src/dataToEsm.ts
index 710f173..01cd4a3 100644
--- a/src/dataToEsm.ts
+++ b/src/dataToEsm.ts
@@ -3,6 +3,10 @@ import { DataToEsm } from './pluginutils';
 
 export type Indent = string | null | undefined;
 
+function stringify(obj: any): string {
+	return (JSON.stringify(obj) || 'undefined').replace(/[\u2028\u2029]/g, char => `\\u${('000' + char.charCodeAt(0).toString(16)).slice(-4)}`);
+}
+
 function serializeArray<T>(arr: Array<T>, indent: Indent, baseIndent: string): string {
 	let output = '[';
 	const separator = indent ? '\n' + baseIndent + indent : '';
@@ -19,7 +23,7 @@ function serializeObject<T>(obj: { [key: string]: T }, indent: Indent, baseInden
 	const keys = Object.keys(obj);
 	for (let i = 0; i < keys.length; i++) {
 		const key = keys[i];
-		const stringKey = makeLegalIdentifier(key) === key ? key : JSON.stringify(key);
+		const stringKey = makeLegalIdentifier(key) === key ? key : stringify(key);
 		output += `${i > 0 ? ',' : ''}${separator}${stringKey}:${indent ? ' ' : ''}${serialize(
 			obj[key],
 			indent,
@@ -31,13 +35,15 @@ function serializeObject<T>(obj: { [key: string]: T }, indent: Indent, baseInden
 
 function serialize(obj: any, indent: Indent, baseIndent: string): string {
 	if (obj === Infinity) return 'Infinity';
+	if (obj === -Infinity) return '-Infinity';
+	if (obj === 0 && 1/obj === -Infinity) return '-0';
 	if (obj instanceof Date) return 'new Date(' + obj.getTime() + ')';
 	if (obj instanceof RegExp) return obj.toString();
-	if (typeof obj === 'number' && isNaN(obj)) return 'NaN';
+	if (obj !== obj) return 'NaN';
 	if (Array.isArray(obj)) return serializeArray(obj, indent, baseIndent);
 	if (obj === null) return 'null';
 	if (typeof obj === 'object') return serializeObject(obj, indent, baseIndent);
-	return JSON.stringify(obj);
+	return stringify(obj);
 }
 
 const dataToEsm: DataToEsm = function dataToEsm(data, options = {}) {
@@ -50,9 +56,14 @@ const dataToEsm: DataToEsm = function dataToEsm(data, options = {}) {
 		options.namedExports === false ||
 		typeof data !== 'object' ||
 		Array.isArray(data) ||
+		data instanceof Date ||
+		data instanceof RegExp ||
 		data === null
-	)
-		return `export default${_}${serialize(data, options.compact ? null : t, '')};`;
+	) {
+		const code = serialize(data, options.compact ? null : t, '');
+		const __ = _ || (/^[{[\-\/]/.test(code) ? '' : ' ');
+		return `export default${__}${code};`;
+	}
 
 	let namedExportCode = '';
 	const defaultExportRows = [];
@@ -69,7 +80,7 @@ const dataToEsm: DataToEsm = function dataToEsm(data, options = {}) {
 			)};${n}`;
 		} else {
 			defaultExportRows.push(
-				`${JSON.stringify(key)}: ${serialize(data[key], options.compact ? null : t, '')}`
+				`${stringify(key)}:${_}${serialize(data[key], options.compact ? null : t, '')}`
 			);
 		}
 	}
diff --git a/src/makeLegalIdentifier.ts b/src/makeLegalIdentifier.ts
index f2d8334..04df298 100644
--- a/src/makeLegalIdentifier.ts
+++ b/src/makeLegalIdentifier.ts
@@ -15,7 +15,7 @@ export const makeLegalIdentifier: MakeLegalIdentifier = function makeLegalIdenti
 		str = `_${str}`;
 	}
 
-	return str;
+	return str || '_';
 };
 
 export { makeLegalIdentifier as default };
diff --git a/test/dataToEsm.test.ts b/test/dataToEsm.test.ts
index 1bd56fa..ff74cbf 100644
--- a/test/dataToEsm.test.ts
+++ b/test/dataToEsm.test.ts
@@ -15,8 +15,8 @@ describe('dataToEsm', function() {
 
 	it('supports non-JSON data', function() {
 		const date = new Date();
-		expect(dataToEsm({ inf: Infinity, date, number: NaN, regexp: /.*/ })).toEqual(
-			'export var inf = Infinity;\nexport var date = new Date(' +
+		expect(dataToEsm({ inf: -Infinity, date, number: NaN, regexp: /.*/ })).toEqual(
+			'export var inf = -Infinity;\nexport var date = new Date(' +
 				date.getTime() +
 				');\nexport var number = NaN;\nexport var regexp = /.*/;\nexport default {\n\tinf: inf,\n\tdate: date,\n\tnumber: number,\n\tregexp: regexp\n};\n'
 		);
@@ -28,11 +28,11 @@ describe('dataToEsm', function() {
 		).toEqual('export var some="data";export var another="data";export default{some,another};');
 		expect(
 			dataToEsm(
-				{ some: { deep: { object: 'definition', here: 'here' } }, another: 'data' },
+				{ some: { deep: { object: 'definition', here: 'here' } }, else: { deep: { object: 'definition', here: 'here' } } },
 				{ compact: true, objectShorthand: false }
 			)
 		).toEqual(
-			'export var some={deep:{object:"definition",here:"here"}};export var another="data";export default{some:some,another:another};'
+			'export var some={deep:{object:"definition",here:"here"}};export default{some:some,"else":{deep:{object:"definition",here:"here"}}};'
 		);
 	});
 
@@ -67,7 +67,7 @@ describe('dataToEsm', function() {
 	});
 
 	it('exports default only for null', function() {
-		expect(dataToEsm(null)).toEqual('export default null;');
+		expect(dataToEsm(null, { compact: true })).toEqual('export default null;');
 	});
 
 	it('exports default only for primitive values', function() {
@@ -79,4 +79,10 @@ describe('dataToEsm', function() {
 			'export var a = "x";\nexport default {\n\ta: a,\n' + '\t"": "y"\n};\n'
 		);
 	});
+
+	it('avoid U+2029 U+2029 -0 be ignored by JSON.stringify, and avoid it return non-string (undefined) before replacing', function() {
+		expect(dataToEsm([-0, '\u2028\u2029', undefined, function() {}], { compact: true })).toEqual(
+			'export default[-0,"\\u2028\\u2029",undefined,undefined];'
+		);
+	});
 });
diff --git a/test/makeLegalIdentifier.test.ts b/test/makeLegalIdentifier.test.ts
index b8002b9..be741cb 100644
--- a/test/makeLegalIdentifier.test.ts
+++ b/test/makeLegalIdentifier.test.ts
@@ -12,4 +12,8 @@ describe('makeLegalIdentifier', function() {
 	it('blacklists arguments (https://github.com/rollup/rollup/issues/871)', function() {
 		expect(makeLegalIdentifier('arguments')).toEqual('_arguments');
 	});
+
+	it('empty', function() {
+		expect(makeLegalIdentifier('')).toEqual('_');
+	});
 });