Intro to JS in functional programming

Author: imteekay

javascript/composing_software/intro_to_js.js

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+// const instead of let and var most of the time
+const number = 1;
+
+const arr = [1, 2, 3];
+
+// `const obj = { a: a }` but we have a better way to do it
+const a = "a";
+const objA = { a };
+
+const b = "b";
+const objB = { b };
+
+// composing objects with object spread operator
+const ab = { ...objA, ...objB }; // { a: 'a', b: 'b' }
+
+// Destructuring arrays
+const [a, b] = ["a", "b"];
+a; // 'a'
+b; // 'b'
+
+// destructuring objects
+const { one } = { one: 1 };
+one; // 1
+
+// but also do multiple destructuring
+const action = { type: "SUM", data: 1 };
+const { type, data } = action;
+
+// we can use this technique in reducers
+const reducer = (state = 0, action = {}) => {
+  const { type, data } = action;
+
+  switch (type) {
+    case "SUM":
+      return state + data;
+    default:
+      return state;
+  }
+};