Chapter 8 Exercises

Chapter 8 - Bugs and Errors/Retry.js

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+/*
+Retry
+- You have a function primitiveMultiply: in 20 percent of cases multiplies two numbers and in the other 80 percent
+of cases raises an exception of type MultiplicatorUnitFailure
+- Write a function that wraps this clunky function and just keeps trying until a call succeeds,
+after which it returns the result.
+
+Make sure you handle only the exceptions you are trying to handle.
+ */
+
+const primitiveMultiply = (numberOne, numberTwo) => {
+    let randomPercentage = Math.floor(Math.random() * 100) + 1;
+    if (randomPercentage <= 20) { return numberOne * numberTwo }
+    else throw new Error("MultiplicatorUnitFailure");
+};
+
+const retry = () => {
+    let result = undefined;
+    while (result === undefined){
+        try{
+            result = primitiveMultiply(2,4);
+        } catch(error){
+            if(error === "MultiplicatorUnitFailure");
+            continue;
+        }
+    }
+    return result;
+}

Chapter 8 - Bugs and Errors/TheLockedBox.js

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+/*
+The Locked Box
+
+Consider the object "box":
+
+const box = {
+   locked: true,
+   unlock() { this.locked = false; },
+   lock() { this.locked = true; },
+   _content: [],
+   get content() {
+     if (this.locked) throw new Error("Locked!");
+     return this._content;
+   }
+};
+
+It is a box with a lock.
+There is an array in the box, but you can get at it only when the box is unlocked.
+Directly accessing the private _content property is forbidden.
+
+- Write a function called withBoxUnlocked that takes a function value as argument,
+unlocks the box, runs the function, and then ensures that the box is locked again before returning,
+regardless of whether the argument function returned normally or threw an exception.
+- For extra points, make sure that if you call withBoxUnlocked when the box is already unlocked,
+the box stays unlocked.
+ */
+
+const box = {
+    locked: true,
+    unlock() { this.locked = false; },
+    lock() { this.locked = true; },
+    _content: [],
+    get content() {
+        if (this.locked) throw new Error("Locked!");
+        return this._content;
+    }
+};
+
+
+function withBoxUnlocked(body){
+    console.log("At the beginning box is locked: " + box.locked);
+    let boxInitialStatus = box.locked;
+    if (box.locked){
+        box.unlock();
+    }
+    try {
+        body();
+    } catch (e) {
+        console.log("Error Raised: ", e)
+    } finally {
+        if (boxInitialStatus === true) box.lock();
+    }
+    console.log("At the end box is locked: " + box.locked);
+}
+
+withBoxUnlocked(function (){
+   box.content.push("gold piece");
+});
+
+try {
+    withBoxUnlocked(function() {
+        throw new Error("Pirates on the horizon! Abort!");
+    });
+
+} catch (e) {
+    console.log("Error raised:", e);
+}