fix: print undefined in the message, closes #38

__tests__/serialize-test.ts

@@ -62,3 +62,17 @@ describe('gives context to non-serializable objects', function() {
     }).toThrowErrorMatchingSnapshot()
   })
 })
+
+describe('null is different from undefined', function() {
+  const foo: any = function foo() {
+    const a = undefined
+    const b = null
+    lazyAss(a === b, a, '!==', b)
+  }
+
+  it('null in the message', function() {
+    expect(function() {
+      foo()
+    }).toThrowError(`undefined !== null`)
+  })
+})

package.json

@@ -91,7 +91,7 @@
     "pkgfiles": "pkgfiles",
     "pretest": "npm run build",
     "semantic-release": "semantic-release",
-    "size": "tarball=\"$(npm pack .)\"; wc -c \"${tarball}\"; tar tvf \"${tarball}\"; rm \"${tarball}\";",
+    "size": "npm pack --dry",
     "test": "npm run unit && npm run jest",
     "unit": "mocha test/commonjs.spec.js",
     "jest": "jest",

src/index.ts

@@ -45,6 +45,12 @@ function replacer(key, value) {
 }
 
 function toString(arg, k) {
+  if (arg === null) {
+    return 'null'
+  }
+  if (arg === undefined) {
+    return 'undefined'
+  }
   if (isPrimitive(arg)) {
     return JSON.stringify(arg)
   }