tag: Javascript

Destructuring is useful but what if you have conflicts with the variable names provided by the object being imported? Consider the following example where we destructure arguments of a function. const getSum = nums => { let { x, y } = { ...nums }; return x + y; }; console.log(getSum({ x: 1, y: 9 })); //10 We can get into a pickle if the function already has a variable x. Well, not exactly in the above example but in a real world program that tends to have a hundred lines of code, and interact with a thousand other components. ...

Specifying one or more arguments as required is one of the common patterns in Javascript. We will see one of the ways in which we can (arguably) make it more simple. Consider the function below - function getSum(x, y) { return x + y; } console.log(getSum()); // NaN We typically check arguments within function where necessary .. function getSum(x, y) { if (!x || !y) throw "Either x or y is empty. Provide valid values."; return x + y; } console.log(getSum()); // Either x or y is empty. Provide valid values. A simpler way to accomplish the same result - ...

Conditional statements and objects - are we talking about the same thing here? Do they have anything in common? Not quite similar, but you could simplify your conditional statements using objects. Consider the below tax rate calculation logic - const incomeLevel = "high"; let taxRate; if (incomeLevel == "very low") { taxRate = income * 0.1; } else if (incomeLevel == "low") { tax = income * 0.3; } else if (incomeLevel == "medium") { taxRate = income * 0.4; } else taxRate = 0; console.log("tax rate:", taxRate); // 0 The multiple ifs can be avoided by using a simple object - const incomeLevel = "very low"; const taxRateRef = { "very low": 0.1, low: 0.3, medium: 0.4, high: 0 }; const taxRate = taxRateRef[incomeLevel]; console.log("tax:", taxRate); // 0.1 Both objects and arrays alike find a lot of use in real-world scenarios to avoid complex loops. They also keep code simple, readable and maintainable.

When should use maps? What are maps anyway? Using an object is cool. We do it all the time - const earth = { name: "earth", position: 3 }; What if we do not have all props at once, but rather incrementally assign props. const earth = { name: "earth", position: 3 }; for (ele in earth) { console.log(ele); } /* output name position */ The order of elements in an object is not guaranteed to be the same as provided in input. This is where a map comes in. Although technically a map is just an instance of an object, it differs in that a map maintains the input order of its elements. ...

Javascript does not have goto - thankfully. But it has continue and break that more or less perform the same function. If for any reason you want to jump out of a loop, here’s how you can do that - for (let i = 0; i < 10; i++) { console.log("i is", i); if (i > 1) break; } But, what if you want to jump to a particular statement? That’s where break can help. outerloop: for (let i = 0; i < 10; i++) { console.log("i is", i); innerloop: for (let j = 0; j < 10; j++) { console.log("j is", j); if (j > 1) break outerloop; } } /* output i is 0 j is 0 j is 1 j is 2 */ Similar to break, you can use continue to continue loop. ...

Use workers when doing lot of work that can be spawned off in another “thread”. How do you open parallel work threads today? Possibly using async functions? Async functions do not block the main thread but allow processing to take place in parallel. Well, almost in parallel - see how event loops work. Although async functions are non-blocking, the call back functions included therein do block the thread. One of the ways of managing truly async functions is through “workers”. ...

Cloning objects is easier than ever before, but you have to remember a few nuances. We will discuss about two ways to clone/copy an object - Deep copy: copy object so that any subsequent changes to new object does not reflect in older object Shallow copy: copy props and child objects of an object, but the new object keeps pointing to the original Both have their uses. Spread operator The quickest way to deep copy is using the spread ... operator. ...

Why is my function returning undefined when I have not mentioned that anywhere. The crux of the issue is in the topic header. All functions have to return something. If nothing is specified, they return undefined. function doSomething() { // do something } const something = doSomething(); console.log("something: ", something); // undefined You may however chose to ignore receiving something from the function. function doSomething() { // do something } doSomething(); Typically, I like to return at least a true or false - just for the heck of it. That’s overengineering to some, but that’s ok. ...

Does JSON.stringify() have anything to do in debugging statements today? There were many Javascript-like systems that did not have the same tooling or debugging methods. I do not quite remember having browsers or ’node’ print out the entire object back in the day - I may be wrong. So it was that I had to use console quite a bit, and what better way to print objects other than converting them to strings? I used JSON.stringify() a lot. ...

You should use strict mode everywhere, but what about inherited code? Typically, you designate strict mode at the beginning of the module - "use strict"; But the module and its friends may have millions of lines of code that you did not write and do not have time to fix. If you introduce "use strict" globally (i.e., at the beginning of the module), you start seeing all those errors here and now. ...