Mefistophell · July 24, 2024 11:38 · Jul 24, 2024 · Jul 24, 2024 · Jul 24, 2024 · Jul 24, 2024
diff --git a/ts_useful_types.ts → ts_useful_features.ts b/ts_useful_types.ts → ts_useful_features.ts
@@ -1,4 +1,6 @@
-/** NoInfer type */
+/** 
+  NoInfer type 
+*/
 function createStreetLight<C extends string>(
   colors: C[],
   defaultColor?: NoInfer<C>,
@@ -10,9 +12,12 @@ createStreetLight(["red", "yellow", "green"], "blue");  // Error
 
 /* ************************************************** */
 
-/** as const */
-// Works with no types referenced or declared.
-// We only needed a single const assertion.
+/** 
+  as const 
+
+  Works with no types referenced or declared.
+  We only needed a single const assertion.
+*/
 function getShapes() {
   let result = [
     { kind: "circle", radius: 100 },
@@ -36,8 +41,11 @@ type T0 = Extract<"a" | "b" | "c", "a" | "f">; // a
 
 /* ************************************************** */
 
-/** Not-null assertion */
-// Compiled with --strictNullChecks
+/** 
+  Not-null assertion 
+
+  Compiled with --strictNullChecks
+*/
 function validateEntity(e?: Entity) {
   // Throw exception if e is null or invalid entity
 }
@@ -48,7 +56,9 @@ function processEntity(e?: Entity) {
 
 /* ************************************************** */
 
-/** Object.groupBy and Map.groupBy */
+/** 
+  Object.groupBy and Map.groupBy 
+*/
 const array = [0, 1, 2, 3, 4, 5];
 const myObj = Object.groupBy(array, (num, index) => {
     return num % 2 === 0 ? "even": "odd";
@@ -69,14 +79,14 @@ myObj.set("odd", [1, 3, 5]);
 
 /* ************************************************** */
 
-/** AsyncDisposable and using 
+/** 
+  AsyncDisposable and using 
 
-Sometimes we have a need to do clean-up after our unit completed its job, this can be: deleting of temp files, 
+  Sometimes we have a need to do clean-up after our unit completed its job, this can be: deleting of temp files, 
 closing network connections, free up some memory. 
 
-New keyword `using` applied to a variable gets its Symbol.dispose or Symbol.asyncDispose method 
+  New keyword `using` applied to a variable gets its Symbol.dispose or Symbol.asyncDispose method 
 to be called at the end of the scope. 
-
 */
 
 async function doWork() {
@@ -114,16 +124,16 @@ func();
 // Disposing (async) b
 // Disposing (async) a
 
-/** DisposableStack and using 
+/** 
+  DisposableStack and using 
 
-useful for doing both one-off clean-up, along with arbitrary amounts of cleanup.
+  useful for doing both one-off clean-up, along with arbitrary amounts of cleanup.
 
-A DisposableStack is a Disposable object that has several methods for keeping track of Disposable objects, 
+  A DisposableStack is a Disposable object that has several methods for keeping track of Disposable objects, 
 and can be given functions for doing arbitrary clean-up work.
 
-Method defer has a callback that will be called once cleanup is disposed.
-Once a resource is created is should be disposed. 
-
+  Method defer has a callback that will be called once cleanup is disposed.
+  Once a resource is created is should be disposed. 
 */
 function doSomeWork() {
     const path = ".some_temp_file";
@@ -142,7 +152,7 @@ function doSomeWork() {
 }
 
 /**
-Decorator metadata:
-Exampe of this is here: 
-https://gist.github.com/Mefistophell/07d63b44d69d38af9406bc59a35c3ec7
+  Decorator metadata:
+  Exampe of this is here: 
+  https://gist.github.com/Mefistophell/07d63b44d69d38af9406bc59a35c3ec7
 */
diff --git a/ts_useful_types.ts b/ts_useful_types.ts
@@ -142,9 +142,7 @@ function doSomeWork() {
 }
 
 /**
-Decorators metadata
+Decorator metadata:
 Exampe of this is here: 
-
-!(ts-decorator-metadata)[https://gist.github.com/Mefistophell/07d63b44d69d38af9406bc59a35c3ec7]
-
+https://gist.github.com/Mefistophell/07d63b44d69d38af9406bc59a35c3ec7
 */
diff --git a/ts_useful_types.ts b/ts_useful_types.ts
@@ -141,10 +141,10 @@ function doSomeWork() {
     // ...
 }
 
-/* 
+/**
 Decorators metadata
 Exampe of this is here: 
 
 !(ts-decorator-metadata)[https://gist.github.com/Mefistophell/07d63b44d69d38af9406bc59a35c3ec7]
 
-/*
+*/
diff --git a/ts_useful_types.ts b/ts_useful_types.ts
@@ -145,4 +145,6 @@ function doSomeWork() {
 Decorators metadata
 Exampe of this is here: 
 
-!(ts-decorator-metadata)[https://gist.github.com/Mefistophell/07d63b44d69d38af9406bc59a35c3ec7]
+!(ts-decorator-metadata)[https://gist.github.com/Mefistophell/07d63b44d69d38af9406bc59a35c3ec7]
+
+/*
diff --git a/ts_useful_types.ts b/ts_useful_types.ts
@@ -144,4 +144,5 @@ function doSomeWork() {
 /* 
 Decorators metadata
 Exampe of this is here: 
-https://www.typescriptlang.org/play/?#code/PTAEEEDsHsBcAsCmAnUB3AhgT1ASwM6izSgCu+ioAxtJPrKBcrhgDa4BeGARq4oQF5QAZSwBbbtFYAKAJQBuAFA06DJi3Zde-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-Dh3QXIxhBZXxfXwKlHl3Y+zoECW7DYJfvu6LkPAD6whqQpbjKuz7IGRyOKUkBylg0jevC+yII8DjOK4PyeEa55pBGYAAAKwPgAC0uA+DAyCUGCyYMM+q4YLovIYcUMJMcgpCuGUfiiBIUhPsurEBAO6SRnK0bCXG5AdkmtApkB47sSxxZdjCpYnO6N5VjWBHev41ZZHsx7tvMobpExqZ7mpQgaWuABkzmTnp2hinO0hORg-7pDJ0jaqp-C4qCF5pISxKgKSNqUmUtLpiQQoisghBiDcZgduguAIKApFXh64r+WkMqbLZ1gYLgyDCF4xkTiFYoZdY0jSFlWCPHWPi4gIQREWatmGgA0ogOBCAAUsIADy6ZwnVvgoW1o0lQNylqF4ABqbCkJQE3TbNXWLWhfKYYZzxYLIfjtQEK2bPRsCkMgjoAAYACTAsNo1So872GltrA7VKz3WaVK33Y9L3AqA72VdVtVGmKjgApAtIeBKUqgEDSjhsokyEAACqKRzhekbZpbA36dfNPgg6AkwU1mVNGpJaQFbpmiIGCGB3I8kCkKlihgmzboc2Cc6gLsrCsN+cj9Xd3QQ6Ab3AggBAwmT9Dfhj72q2K9Na8D0pgsQk0zbLJMXuDT2gIhtCLbrkoAeVa28fx1IawzQpM8ZHj64zRm+B43NYTF-PcCgYX4ukuvq9VmtZuxHvflHkXwGrftakIGecxFRBp2KwfscHRvhhVROOno1qE2ltDSAA5OA7DFHXHh18IyosC3oAACySsoylSIgMKsNAPjSP6SEwib+1yLIQA
+
+!(ts-decorator-metadata)[https://gist.github.com/Mefistophell/07d63b44d69d38af9406bc59a35c3ec7]
diff --git a/ts_useful_types.ts b/ts_useful_types.ts
@@ -139,4 +139,9 @@ function doSomeWork() {
         return;
     }
     // ...
-}
+}
+
+/* 
+Decorators metadata
+Exampe of this is here: 
+https://www.typescriptlang.org/play/?#code/PTAEEEDsHsBcAsCmAnUB3AhgT1ASwM6izSgCu+ioAxtJPrKBcrhgDa4BeGARq4oQF5QAZSwBbbtFYAKAJQBuAFA06DJi3Zde-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-Dh3QXIxhBZXxfXwKlHl3Y+zoECW7DYJfvu6LkPAD6whqQpbjKuz7IGRyOKUkBylg0jevC+yII8DjOK4PyeEa55pBGYAAAKwPgAC0uA+DAyCUGCyYMM+q4YLovIYcUMJMcgpCuGUfiiBIUhPsurEBAO6SRnK0bCXG5AdkmtApkB47sSxxZdjCpYnO6N5VjWBHev41ZZHsx7tvMobpExqZ7mpQgaWuABkzmTnp2hinO0hORg-7pDJ0jaqp-C4qCF5pISxKgKSNqUmUtLpiQQoisghBiDcZgduguAIKApFXh64r+WkMqbLZ1gYLgyDCF4xkTiFYoZdY0jSFlWCPHWPi4gIQREWatmGgA0ogOBCAAUsIADy6ZwnVvgoW1o0lQNylqF4ABqbCkJQE3TbNXWLWhfKYYZzxYLIfjtQEK2bPRsCkMgjoAAYACTAsNo1So872GltrA7VKz3WaVK33Y9L3AqA72VdVtVGmKjgApAtIeBKUqgEDSjhsokyEAACqKRzhekbZpbA36dfNPgg6AkwU1mVNGpJaQFbpmiIGCGB3I8kCkKlihgmzboc2Cc6gLsrCsN+cj9Xd3QQ6Ab3AggBAwmT9Dfhj72q2K9Na8D0pgsQk0zbLJMXuDT2gIhtCLbrkoAeVa28fx1IawzQpM8ZHj64zRm+B43NYTF-PcCgYX4ukuvq9VmtZuxHvflHkXwGrftakIGecxFRBp2KwfscHRvhhVROOno1qE2ltDSAA5OA7DFHXHh18IyosC3oAACySsoylSIgMKsNAPjSP6SEwib+1yLIQA
diff --git a/ts_useful_types.ts b/ts_useful_types.ts
@@ -114,7 +114,17 @@ func();
 // Disposing (async) b
 // Disposing (async) a
 
-/** DisposableStack and using */
+/** DisposableStack and using 
+
+useful for doing both one-off clean-up, along with arbitrary amounts of cleanup.
+
+A DisposableStack is a Disposable object that has several methods for keeping track of Disposable objects, 
+and can be given functions for doing arbitrary clean-up work.
+
+Method defer has a callback that will be called once cleanup is disposed.
+Once a resource is created is should be disposed. 
+
+*/
 function doSomeWork() {
     const path = ".some_temp_file";
     const file = fs.openSync(path, "w+");

diff --git a/ts_useful_types.ts b/ts_useful_types.ts
@@ -69,7 +69,16 @@ myObj.set("odd", [1, 3, 5]);
 
 /* ************************************************** */
 
-/** AsyncDisposable and using */
+/** AsyncDisposable and using 
+
+Sometimes we have a need to do clean-up after our unit completed its job, this can be: deleting of temp files, 
+closing network connections, free up some memory. 
+
+New keyword `using` applied to a variable gets its Symbol.dispose or Symbol.asyncDispose method 
+to be called at the end of the scope. 
+
+*/
+
 async function doWork() {
     // Do fake work for half a second.
     await new Promise(resolve => setTimeout(resolve, 500));

diff --git a/ts_useful_types.ts b/ts_useful_types.ts
@@ -67,4 +67,57 @@ const myObj = new Map();
 myObj.set("even", [0, 2, 4]);
 myObj.set("odd", [1, 3, 5]);
 
-/* ************************************************** */
+/* ************************************************** */
+
+/** AsyncDisposable and using */
+async function doWork() {
+    // Do fake work for half a second.
+    await new Promise(resolve => setTimeout(resolve, 500));
+}
+function loggy(id: string): AsyncDisposable {
+    console.log(`Constructing ${id}`);
+    return {
+        async [Symbol.asyncDispose]() {
+            console.log(`Disposing (async) ${id}`);
+            await doWork();
+        },
+    }
+}
+async function func() {
+    await using a = loggy("a");
+    await using b = loggy("b");
+    {
+        await using c = loggy("c");
+        await using d = loggy("d");
+    }
+    await using e = loggy("e");
+    return;
+}
+func();
+// Constructing a
+// Constructing b
+// Constructing c
+// Constructing d
+// Disposing (async) d
+// Disposing (async) c
+// Constructing e
+// Disposing (async) e
+// Disposing (async) b
+// Disposing (async) a
+
+/** DisposableStack and using */
+function doSomeWork() {
+    const path = ".some_temp_file";
+    const file = fs.openSync(path, "w+");
+    using cleanup = new DisposableStack();
+    cleanup.defer(() => {
+        fs.closeSync(file);
+        fs.unlinkSync(path);
+    });
+    // use file...
+    if (someCondition()) {
+        // do some more work...
+        return;
+    }
+    // ...
+}
diff --git a/ts_useful_types.ts b/ts_useful_types.ts
@@ -8,6 +8,7 @@ function createStreetLight<C extends string>(
 createStreetLight(["red", "yellow", "green"], "red");  // OK
 createStreetLight(["red", "yellow", "green"], "blue");  // Error
 
+/* ************************************************** */
 
 /** as const */
 // Works with no types referenced or declared.
@@ -33,6 +34,7 @@ type T0 = NonNullable<string | number | undefined>; // string | number
 type T0 = ReturnType<() => string>; // string
 type T0 = Extract<"a" | "b" | "c", "a" | "f">; // a
 
+/* ************************************************** */
 
 /** Not-null assertion */
 // Compiled with --strictNullChecks
@@ -42,4 +44,27 @@ function validateEntity(e?: Entity) {
 function processEntity(e?: Entity) {
   validateEntity(e);
   let s = e!.name; // Assert that e is non-null and access name
-}
+}
+
+/* ************************************************** */
+
+/** Object.groupBy and Map.groupBy */
+const array = [0, 1, 2, 3, 4, 5];
+const myObj = Object.groupBy(array, (num, index) => {
+    return num % 2 === 0 ? "even": "odd";
+});
+// equivalent to 
+const myObj = {
+    even: [0, 2, 4],
+    odd: [1, 3, 5],
+};
+
+const myObj = Map.groupBy(array, (num, index) => {
+    return num % 2 === 0 ? "even" : "odd";
+});
+// equivalent to 
+const myObj = new Map();
+myObj.set("even", [0, 2, 4]);
+myObj.set("odd", [1, 3, 5]);
+
+/* ************************************************** */
diff --git a/ts_useful_types.ts b/ts_useful_types.ts
@@ -31,4 +31,15 @@ for (const shape of getShapes()) {
 
 type T0 = NonNullable<string | number | undefined>; // string | number
 type T0 = ReturnType<() => string>; // string
-type T0 = Extract<"a" | "b" | "c", "a" | "f">; // a
+type T0 = Extract<"a" | "b" | "c", "a" | "f">; // a
+
+
+/** Not-null assertion */
+// Compiled with --strictNullChecks
+function validateEntity(e?: Entity) {
+  // Throw exception if e is null or invalid entity
+}
+function processEntity(e?: Entity) {
+  validateEntity(e);
+  let s = e!.name; // Assert that e is non-null and access name
+}
diff --git a/example.ts → ts_useful_types.ts b/example.ts → ts_useful_types.ts
diff --git a/example.ts b/example.ts
@@ -0,0 +1,34 @@
+/** NoInfer type */
+function createStreetLight<C extends string>(
+  colors: C[],
+  defaultColor?: NoInfer<C>,
+) {
+  // ...
+}
+createStreetLight(["red", "yellow", "green"], "red");  // OK
+createStreetLight(["red", "yellow", "green"], "blue");  // Error
+
+
+/** as const */
+// Works with no types referenced or declared.
+// We only needed a single const assertion.
+function getShapes() {
+  let result = [
+    { kind: "circle", radius: 100 },
+    { kind: "square", sideLength: 50 },
+  ] as const;
+  return result;
+}
+for (const shape of getShapes()) {
+  // Narrows perfectly!
+  if (shape.kind === "circle") {
+    console.log("Circle radius", shape.radius);
+  } else {
+    console.log("Square side length", shape.sideLength);
+  }
+}
+
+
+type T0 = NonNullable<string | number | undefined>; // string | number
+type T0 = ReturnType<() => string>; // string
+type T0 = Extract<"a" | "b" | "c", "a" | "f">; // a
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