Add Mutable.

Author: mbostock

package.json

@@ -11,15 +11,15 @@
     "url": "https://github.com/observablehq/notebook-stdlib.git"
   },
   "scripts": {
-    "test": "tape -r @std/esm 'test/**/*-test.js'",
+    "test": "tape -r esm 'test/**/*-test.js'",
     "precommit": "eslint . && yarn test"
   },
-  "@std/esm": {
-    "esm": "js",
+  "esm": {
+    "mode": "all",
     "cjs": true
   },
   "dependencies": {
-    "@std/esm": "^0.16.0",
+    "esm": "^3.0.5",
     "d3-require": "^0.6.6"
   },
   "devDependencies": {

src/index.js

@@ -1,31 +1,2 @@
-import {resolve as resolveDefault, requireFrom} from "d3-require";
-import constant from "./constant";
-import DOM from "./dom/index";
-import Files from "./files/index";
-import Generators from "./generators/index";
-import html from "./html";
-import md from "./md";
-import now from "./now";
-import Promises from "./promises/index";
-import svg from "./svg";
-import tex from "./tex";
-import width from "./width";
-
-export default function Library(resolve) {
-  if (resolve == null) resolve = resolveDefault;
-  var require = requireFrom(resolve);
-  Object.defineProperties(this, {
-    DOM: {value: DOM, enumerable: true},
-    Files: {value: Files, enumerable: true},
-    Generators: {value: Generators, enumerable: true},
-    Promises: {value: Promises, enumerable: true},
-    require: {value: constant(require), enumerable: true},
-    resolve: {value: constant(resolve), enumerable: true},
-    html: {value: constant(html), enumerable: true},
-    md: {value: md(require, resolve), enumerable: true},
-    svg: {value: constant(svg), enumerable: true},
-    tex: {value: tex(require, resolve), enumerable: true},
-    now: {value: now, enumerable: true},
-    width: {value: width, enumerable: true}
-  });
-}
+export {default as Library} from "./library";
+export {default as Mutable} from "./mutable";

src/library.js

@@ -0,0 +1,31 @@
+import {resolve as resolveDefault, requireFrom} from "d3-require";
+import constant from "./constant";
+import DOM from "./dom/index";
+import Files from "./files/index";
+import Generators from "./generators/index";
+import html from "./html";
+import md from "./md";
+import now from "./now";
+import Promises from "./promises/index";
+import svg from "./svg";
+import tex from "./tex";
+import width from "./width";
+
+export default function Library(resolve) {
+  if (resolve == null) resolve = resolveDefault;
+  var require = requireFrom(resolve);
+  Object.defineProperties(this, {
+    DOM: {value: DOM, enumerable: true},
+    Files: {value: Files, enumerable: true},
+    Generators: {value: Generators, enumerable: true},
+    Promises: {value: Promises, enumerable: true},
+    require: {value: constant(require), enumerable: true},
+    resolve: {value: constant(resolve), enumerable: true},
+    html: {value: constant(html), enumerable: true},
+    md: {value: md(require, resolve), enumerable: true},
+    svg: {value: constant(svg), enumerable: true},
+    tex: {value: tex(require, resolve), enumerable: true},
+    now: {value: now, enumerable: true},
+    width: {value: width, enumerable: true}
+  });
+}

src/mutable.js

@@ -0,0 +1,19 @@
+import observe from "./generators/observe";
+
+export default function Mutable(value) {
+  let change;
+  Object.defineProperties(this, {
+    generator: {value: observe(_ => change = _)},
+    value: {
+      get: function() { return value; },
+      set: function(x) { return change((value = x)); }
+    }
+  });
+  if (value !== undefined) change(value);
+}
+
+Mutable.value = function(init) {
+  return function() {
+    return new Mutable(init.apply(this, arguments));
+  };
+};

test/index-test.js

@@ -1,5 +1,5 @@
 import tape from "tape-await";
-import Library from "../src/";
+import Library from "../src/library";
 
 tape("new Library returns a library with the expected keys", async test => {
   test.deepEqual(Object.keys(new Library()).sort(), [

yarn.lock

@@ -2,10 +2,6 @@
 # yarn lockfile v1
 
 
-"@std/esm@^0.16.0":
-  version "0.16.0"
-  resolved "https://registry.yarnpkg.com/@std/esm/-/esm-0.16.0.tgz#2a7a33ecb7f1701cebd4c87df6d0d945ed51f730"
-
 abab@^1.0.4:
   version "1.0.4"
   resolved "https://registry.yarnpkg.com/abab/-/abab-1.0.4.tgz#5faad9c2c07f60dd76770f71cf025b62a63cfd4e"
@@ -427,6 +423,10 @@ eslint@^4.12.1:
     table "^4.0.1"
     text-table "~0.2.0"
 
+esm@^3.0.5:
+  version "3.0.25"
+  resolved "https://registry.yarnpkg.com/esm/-/esm-3.0.25.tgz#d374e714c07abe0b8a7e80d18819e5823e491dbd"
+
 espree@^3.5.2:
   version "3.5.2"
   resolved "https://registry.yarnpkg.com/espree/-/espree-3.5.2.tgz#756ada8b979e9dcfcdb30aad8d1a9304a905e1ca"