Merge pull request #36 from davidchambers/lookup

remove defaulting of null and undefined to empty string
davidchambers · May 18, 2018 · 1b1ea4a · 1b1ea4a
2 parents 711dfc8 + d174ab7
commit 1b1ea4a
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Showing 2 changed files with 39 additions and 19 deletions.
diff --git a/index.js b/index.js
@@ -9,11 +9,6 @@ void function(global) {
     return err;
   }
 
-  //  defaultTo :: a,a? -> a
-  function defaultTo(x, y) {
-    return y == null ? x : y;
-  }
-
   //  create :: Object -> String,*... -> String
   function create(transformers) {
     return function(template) {
@@ -43,7 +38,23 @@ void function(global) {
             key = String(idx);
             idx += 1;
           }
-          var value = defaultTo('', lookup(args, key.split('.')));
+
+          //  1.  Split the key into a lookup path.
+          //  2.  If the first path component is not an index, prepend '0'.
+          //  3.  Reduce the lookup path to a single result. If the lookup
+          //      succeeds the result is a singleton array containing the
+          //      value at the lookup path; otherwise the result is [].
+          //  4.  Unwrap the result by reducing with '' as the default value.
+          var path = key.split('.');
+          var value = (/^\d+$/.test(path[0]) ? path : ['0'].concat(path))
+            .reduce(function(maybe, key) {
+              return maybe.reduce(function(_, x) {
+                return x != null && key in Object(x) ?
+                  [typeof x[key] === 'function' ? x[key]() : x[key]] :
+                  [];
+              }, []);
+            }, [args])
+            .reduce(function(_, x) { return x; }, '');
 
           if (xf == null) {
             return value;
@@ -57,19 +68,6 @@ void function(global) {
     };
   }
 
-  function lookup(_obj, _path) {
-    var obj = _obj;
-    var path = _path;
-    if (!/^\d+$/.test(path[0])) {
-      path = ['0'].concat(path);
-    }
-    for (var idx = 0; idx < path.length; idx += 1) {
-      var key = path[idx];
-      obj = typeof obj[key] === 'function' ? obj[key]() : obj[key];
-    }
-    return obj;
-  }
-
   //  format :: String,*... -> String
   var format = create({});
 

diff --git a/test/index.js b/test/index.js
@@ -59,6 +59,13 @@ suite('format', function() {
     );
   });
 
+  test('uses default string representations', function() {
+    eq(format('result: {}', null), 'result: null');
+    eq(format('result: {}', undefined), 'result: undefined');
+    eq(format('result: {}', [1, 2, 3]), 'result: 1,2,3');
+    eq(format('result: {}', {foo: 42}), 'result: [object Object]');
+  });
+
   test('treats "{{" and "}}" as "{" and "}"', function() {
     eq(format('{{ {}: "{}" }}', 'foo', 'bar'), '{ foo: "bar" }');
   });
@@ -75,6 +82,21 @@ suite('format', function() {
     eq(format('{first} {last}', bobby), 'Bobby Fischer');
   });
 
+  test('defaults to "" if lookup fails', function() {
+    eq(format('result: {foo.bar.baz}', null), 'result: ');
+    eq(format('result: {foo.bar.baz}', 'x'), 'result: ');
+    eq(format('result: {foo.bar.baz}', {}), 'result: ');
+    eq(format('result: {foo.bar.baz}', {foo: null}), 'result: ');
+    eq(format('result: {foo.bar.baz}', {foo: 'x'}), 'result: ');
+    eq(format('result: {foo.bar.baz}', {foo: {}}), 'result: ');
+    eq(format('result: {foo.bar.baz}', {foo: {bar: null}}), 'result: ');
+    eq(format('result: {foo.bar.baz}', {foo: {bar: 'x'}}), 'result: ');
+    eq(format('result: {foo.bar.baz}', {foo: {bar: {}}}), 'result: ');
+    eq(format('result: {foo.bar.baz}', {foo: {bar: {baz: null}}}), 'result: null');
+    eq(format('result: {foo.bar.baz}', {foo: {bar: {baz: 'x'}}}), 'result: x');
+    eq(format('result: {foo.bar.baz}', {foo: {bar: {baz: {}}}}), 'result: [object Object]');
+  });
+
   test('invokes methods', function() {
     eq(format('{0.toLowerCase}', 'III'), 'iii');
     eq(format('{0.toUpperCase}', 'iii'), 'III');