Add 7 new snippets

snippets/alphabetical.md

@@ -0,0 +1,29 @@
+---
+title: Sort array alphabetically
+tags: array
+author: chalarangelo
+cover: blog_images/boutique-home-office-1.jpg
+firstSeen: 2023-02-15T05:00:00-04:00
+---
+
+Sorts an array of objects alphabetically based on a given property.
+
+- Use `Array.prototype.sort()` to sort the array based on the given property.
+- Use `String.prototype.localeCompare()` to compare the values for the given property.
+
+```js
+const alphabetical = (arr, getter, order = 'asc') =>
+  arr.sort(
+    order === 'desc'
+      ? (a, b) => getter(b).localeCompare(getter(a))
+      : (a, b) => getter(a).localeCompare(getter(b))
+  );
+```
+
+```js
+const people = [ { name: 'John' }, { name: 'Adam' }, { name: 'Mary' } ];
+alphabetical(people, g => g.name);
+// [ { name: 'Adam' }, { name: 'John' }, { name: 'Mary' } ]
+alphabetical(people, g => g.name, 'desc');
+// [ { name: 'Mary' }, { name: 'John' }, { name: 'Adam' } ]
+```

snippets/intersects.md

@@ -0,0 +1,24 @@
+---
+title: Check if two arrays intersect
+tags: array
+author: chalarangelo
+cover: blog_images/interior-5.jpg
+firstSeen: 2023-02-17T05:00:00-04:00
+---
+
+Determines if two arrays have a common item.
+
+- Create a `Set` from `b` to get the unique values in `b`.
+- Use `Array.prototype.some()` on `a` to check if any of its values are contained in `b`, using `Set.prototype.has()`.
+
+```js
+const intersects = (a, b) => {
+  const s = new Set(b);
+  return [...new Set(a)].some(x => s.has(x));
+};
+```
+
+```js
+intersects(['a', 'b'], ['b', 'c']); // true
+intersects(['a', 'b'], ['c', 'd']); // false
+```

snippets/listify.md

@@ -0,0 +1,27 @@
+---
+title: Map an object to an array
+tags: object,array
+author: chalarangelo
+cover: blog_images/metro-arrival.jpg
+firstSeen: 2023-02-05T05:00:00-04:00
+---
+
+Maps an object to an object array, using the provided mapping function.
+
+- Use `Object.entries()` to get an array of the object's key-value pairs.
+- Use `Array.prototype.reduce()` to map the array to an object.
+- Use `mapFn` to map the keys and values of the object and `Array.prototype.push()` to add the mapped values to the array.
+
+```js
+const listify = (obj, mapFn) =>
+  Object.entries(obj).reduce((acc, [key, value]) => {
+    acc.push(mapFn(key, value));
+    return acc;
+  }, []);
+```
+
+```js
+const people = { John: { age: 42 }, Adam: { age: 39 } };
+listify(people, (key, value) => ({ name: key, ...value }));
+// [ { name: 'John', age: 42 }, { name: 'Adam', age: 39 } ]
+```

snippets/lowerize.md

@@ -0,0 +1,24 @@
+---
+title: Lowercase object keys
+tags: object
+author: chalarangelo
+cover: blog_images/building-facade.jpg
+firstSeen: 2023-02-12T05:00:00-04:00
+---
+
+Converts all the keys of an object to lower case.
+
+- Use `Object.keys()` to get an array of the object's keys.
+- Use `Array.prototype.reduce()` to map the array to an object, using `String.prototype.toLowerCase()` to lowercase the keys.
+
+```js
+const lowerize = obj =>
+  Object.keys(obj).reduce((acc, k) => {
+    acc[k.toLowerCase()] = obj[k];
+    return acc;
+  }, {});
+```
+
+```js
+lowerize({ Name: 'John', Age: 22 }); // { name: 'John', age: 22 }
+```

snippets/objectify.md

@@ -0,0 +1,32 @@
+---
+title: Map an array to an object
+tags: array,object
+author: chalarangelo
+cover: blog_images/metro-tunnel.jpg
+firstSeen: 2023-02-04T05:00:00-04:00
+---
+
+Maps an object array to an object, using the provided mapping functions.
+
+- Use `Array.prototype.reduce()` to map the array to an object.
+- Use `mapKey` to map the keys of the object and `mapValue` to map the values.
+
+```js
+const objectify = (arr, mapKey, mapValue = i => i) =>
+  arr.reduce((acc, item) => {
+    acc[mapKey(item)] = mapValue(item);
+    return acc;
+  }, {});
+```
+
+```js
+const people = [ { name: 'John', age: 42 }, { name: 'Adam', age: 39 } ];
+objectify(people, p => p.name.toLowerCase());
+// { john: { name: 'John', age: 42 }, adam: { name: 'Adam', age: 39 } }
+objectify(
+  people,
+  p => p.name.toLowerCase(),
+  p => p.age
+);
+// { john: 42, adam: 39 }
+```

snippets/replaceOrAppend.md

@@ -0,0 +1,38 @@
+---
+title: Replace or append array value
+tags: array
+author: chalarangelo
+cover: blog_images/boutique-home-office-2.jpg
+firstSeen: 2023-02-19T05:00:00-04:00
+---
+
+Replaces an item in an array or appends it, if it doesn't exist.
+
+- Use the spread operator (`...`) to create a shallow copy of the array.
+- Use `Array.prototype.findIndex()` to find the index of the first element that satisfies the provided comparison function, `compFn`.
+- If no such element is found, use `Array.prototype.push()` to append the new value to the array.
+- Otherwise, use `Array.prototype.splice()` to replace the value at the found index with the new value.
+
+```js
+const replaceOrAppend = (arr, val, compFn) => {
+  const res = [...arr];
+  const i = arr.findIndex(v => compFn(v, val));
+  if (i === -1) res.push(val);
+  else res.splice(i, 1, val);
+  return res;
+};
+```
+
+```js
+const people = [ { name: 'John', age: 30 }, { name: 'Jane', age: 28 } ];
+const jane = { name: 'Jane', age: 29 };
+const jack = { name: 'Jack', age: 28 };
+replaceOrAppend(people, jane, (a, b) => a.name === b.name);
+// [ { name: 'John', age: 30 }, { name: 'Jane', age: 29 } ]
+replaceOrAppend(people, jack, (a, b) => a.name === b.name);
+// [
+//   { name: 'John', age: 30 },
+//   { name: 'Jane', age: 28 },
+//   { name: 'Jack', age: 28 }
+// ]
+```

snippets/upperize.md

@@ -0,0 +1,24 @@
+---
+title: Uppercase object keys
+tags: object
+author: chalarangelo
+cover: blog_images/sofia-tram.jpg
+firstSeen: 2023-02-11T05:00:00-04:00
+---
+
+Converts all the keys of an object to upper case.
+
+- Use `Object.keys()` to get an array of the object's keys.
+- Use `Array.prototype.reduce()` to map the array to an object, using `String.prototype.toUpperCase()` to uppercase the keys.
+
+```js
+const upperize = obj =>
+  Object.keys(obj).reduce((acc, k) => {
+    acc[k.toUpperCase()] = obj[k];
+    return acc;
+  }, {});
+```
+
+```js
+upperize({ Name: 'John', Age: 22 }); // { NAME: 'John', AGE: 22 }
+```