loop tips

Author: lgope

js-coding-technique/loops.js

@@ -0,0 +1,99 @@
+const mil = 1000000;
+const arr = Array(mil);
+
+console.time('⏲️');
+
+for (let i = 0; i < mil; i++) {} // 1.6ms
+
+for (const v of arr) {
+} // 11.7ms
+
+arr.forEach(v => v); // 2.1ms
+
+for (let i = mil; i > 0; i--) {} // 1.5ms
+
+console.timeEnd('⏲️');
+
+const equine = { unicorn: '🦄', horse: '🐴', zebra: '🦓' };
+
+for (const key in equine) {
+  // Filters out properties inherited from prototype
+  if (equine.hasOwnProperty(key)) {
+    console.log(equine[key]);
+  }
+}
+
+// Unwrap the the Values
+
+for (const val of Object.values(equine)) {
+  console.log(val);
+}
+
+// Create a Map
+const equine = new Map(Object.entries(equine));
+
+for (const v of equine.values()) {
+  console.log(v);
+}
+
+const equine = [
+  ['unicorn', '🦄'],
+  ['horse', '🐴'],
+  ['zebra', '🦓'],
+];
+
+// 😒 Meh Code
+for (const arr of equine) {
+  const type = arr[0];
+  const face = arr[1];
+  console.log(`${type} looks like ${face}`);
+}
+
+// 🤯 Destructured Code
+for (const [type, face] of equine) {
+  console.log(`${type} looks like ${face}`);
+}
+
+///////////////
+arr[Symbol.iterator] = function () {
+  let i = 0;
+  let arr = this;
+  return {
+    next: function () {
+      if (i >= arr.length) {
+        return { done: true };
+      } else {
+        const value = arr[i] + '🙉';
+        i++;
+        return { value, done: false };
+      }
+    },
+  };
+};
+
+////////////////////////////////
+
+const faces = ['😀', '😍', '🤤', '🤯', '💩', '🤠', '🥳'];
+
+// Transform values
+const withIndex = faces.map((v, i) => `face ${i} is ${v}`);
+
+// Test at least one value meets a condition
+const isPoopy = faces.some(v => v === '💩');
+// false
+
+// Test all values meet a condition
+const isEmoji = faces.every(v => v > 'ÿ');
+// true
+
+// Filter out values
+const withoutPoo = faces.filter(v => v !== '💩');
+
+// Reduce values to a single value
+const pooCount = faces.reduce((acc, cur) => {
+  return acc + (cur === '💩' ? 1 : 0);
+}, 0);
+console.log(pooCount);
+
+// Sort the values
+const sorted = faces.sort((a, b) => a < b);