Support default values

.gitignore

@@ -1,3 +1,4 @@
 node_modules
 *.log
 .DS_Store
+.vscode

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## [Unreleased][unreleased]
 
+- Support default values
+
 ## [1.0.7][] - 2023-04-29
 
 - Drop node.js 14 support, add node.js 20

README.md

@@ -34,6 +34,29 @@ const templ = t`${'hello'} ${'myFriend'}, great ${'positions'} of Rome`;
 console.log(templ(data));
 ```
 
+With default values provided (optionally):
+
+```js
+const t = require('tickplate');
+
+const data = {
+  greeting: 'Valē!',
+  person: {
+    name: 'Lucius Aurelius Verus',
+    toString() {
+      return this.name;
+    },
+  },
+  positions: ['brother', 'emperor', 'co-emperor'],
+  ruleFrom: 161,
+  ruleTo: 169,
+};
+
+const templ = t`${'greeting='} ${'person="Marcus Aurelius"'}, great ${'positions=["emperor", "philosopher"]'} of Rome from ${'ruleFrom=161'} to ${'ruleTo=180'} AD`;
+
+console.log(templ(data));
+```
+
 ## License & Contributors
 
 Copyright (c) 2017-2023 [Metarhia contributors](https://github.com/metarhia/tickplate/graphs/contributors).

test.js

@@ -4,22 +4,83 @@ const assert = require('node:assert').strict;
 
 const t = require('./tickplate.js');
 
-const data = {
-  hello: 'Ave!',
-  myFriend: {
-    name: 'Marcus Aurelius',
-    toString() {
-      return this.name;
+{
+  ({ description: 'No fallbacks used.' });
+
+  const data = {
+    hello: 'Ave!',
+    myFriend: {
+      name: 'Marcus Aurelius',
+      toString() {
+        return this.name;
+      },
     },
-  },
-  positions: ['imperor', 'philosopher', 'writer'],
-};
-
-const templ = t`${'hello'} ${'myFriend'}, great ${'positions'} of Rome`;
-
-const expect = 'Ave! Marcus Aurelius, great imperor,philosopher,writer of Rome';
-const result = templ(data);
-assert.strictEqual(result, expect);
-assert.strictEqual(templ({ myFriend: 'Hadrian' }), ' Hadrian, great  of Rome');
-assert.strictEqual(templ({ hello: 'Hi!' }), 'Hi! , great  of Rome');
-assert.strictEqual(templ({}), ' , great  of Rome');
+    positions: ['emperor', 'philosopher', 'writer'],
+  };
+
+  const templ = t`${'hello'} ${'myFriend'}, great ${'positions'} of Rome`;
+
+  const expect =
+    'Ave! Marcus Aurelius, great emperor,philosopher,writer of Rome';
+  const result = templ(data);
+  assert.strictEqual(result, expect);
+  assert.strictEqual(
+    templ({ myFriend: 'Hadrian' }),
+    ' Hadrian, great  of Rome',
+  );
+  assert.strictEqual(templ({ hello: 'Hi!' }), 'Hi! , great  of Rome');
+  assert.strictEqual(templ({}), ' , great  of Rome');
+}
+
+{
+  ({
+    description:
+      'Fallback primitives and arrays of primitives provided, with "=" separator, empty spaces around trimmed',
+  });
+
+  const data = {
+    greeting: 'Ave!',
+    person: {
+      name: 'Lucius Verus',
+      toString() {
+        return this.name;
+      },
+    },
+    positions: ['brother', 'emperor', 'co-emperor'],
+    ruleFrom: 161,
+    ruleTo: 169,
+  };
+
+  const templ = t`${'greeting='} ${'person = "Marcus Aurelius"'}, great ${'positions  =["emperor", "philosopher"]'} of Rome from ${'ruleFrom = 161'} to ${'ruleTo=180'} AD`;
+
+  const expect =
+    'Ave! Lucius Verus, great brother,emperor,co-emperor of Rome from 161 to 169 AD';
+  const result = templ(data);
+  assert.strictEqual(result, expect);
+  assert.strictEqual(
+    templ({}),
+    ' Marcus Aurelius, great emperor,philosopher of Rome from 161 to 180 AD',
+  );
+  assert.strictEqual(
+    templ({ greeting: 'Valē!!!', ruleFrom: '44 BC', ruleTo: 2023 }),
+    'Valē!!! Marcus Aurelius, great emperor,philosopher of Rome from 44 BC to 2023 AD',
+  );
+
+  const messedUp = t`${'greeting= /\\/'} ${'person = " "'}, great ${'positions  ="emperor", "philosopher"]]'} of Rome from ${'ruleFrom    = undefined'} to ${'ruleTo==180'} AD`;
+  assert.strictEqual(messedUp(data), expect);
+  assert.strictEqual(messedUp({}), '  , great  of Rome from  to  AD');
+  assert.strictEqual(
+    messedUp({ greeting: 'No way!' }),
+    'No way!  , great  of Rome from  to  AD',
+  );
+  assert.strictEqual(
+    messedUp({
+      greeting: 'Papa Roma is',
+      person: 'a',
+      positions: 'pizzeria',
+      ruleFrom: 1970,
+      ruleTo: 'today',
+    }),
+    'Papa Roma is a, great pizzeria of Rome from 1970 to today AD',
+  );
+}

tickplate.js

@@ -1,14 +1,40 @@
 'use strict';
 
-const tickplate =
-  (strings, ...keys) =>
-  (values) => {
+const SEPARATOR = '=';
+
+const parseKeyValuePair = (value, sep = SEPARATOR) => {
+  const [lhs, ...rhs] = value.split(sep);
+  const key = lhs.trim();
+  if (rhs.length === 0) return { key };
+  const rhsRestored = rhs.join(sep).trim();
+  try {
+    const value = JSON.parse(rhsRestored);
+    return { key, value };
+  } catch {
+    return { key };
+  }
+};
+
+const parseKeys = (strKeyValuePairs, sep = SEPARATOR) => {
+  const defaults = {};
+  for (const pair of strKeyValuePairs) {
+    const { key, value } = parseKeyValuePair(pair, sep);
+    defaults[key] = value;
+  }
+  return { keys: Object.keys(defaults), defaults };
+};
+
+const tickplate = (strings, ...keys) => {
+  const { keys: tickplateKeys, defaults } = parseKeys(keys);
+  return (values) => {
+    const tickplateValues = { ...defaults, ...values };
     const result = [strings[0]];
-    for (let i = 0; i < keys.length; i++) {
-      const key = keys[i];
-      result.push(values[key], strings[i + 1]);
+    for (let i = 0; i < tickplateKeys.length; i++) {
+      const key = tickplateKeys[i];
+      result.push(tickplateValues[key], strings[i + 1]);
     }
     return result.join('');
   };
+};
 
 module.exports = tickplate;