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. ...
There is this myth that assigning array elements is better performant than push. I believe this originated from Javascript of yore, but is not relevant anymore. In fact, today push may be almost equal to or edge out assignment of array elements using keys (depending on runtime engine that is). A quick test Let us do a really quick test - create an array of 1000 elements, assign each element with key compare the performance against just pushing a 1000 elements to a blank array Code below - ...
It is common advise to nullify a prop value within an object rather than deleting the prop. Should you prefer one over the other? Especially, in performance intensive applications. Delete object prop What do you do when you do not need a key-value pair in an object? Why, we simply delete it, of course. const earth = { name: "earth", position: 3, life: true }; console.log(earth); // { name: 'earth', position: 3, life: true } delete earth["life"]; console.log(earth); // { name: 'earth', position: 3 } This is clean and just works. ...
Use values with same types in any array. Changing types (even for scenarios that you think are totally valid for the day) can rain down hell. Homogeneity of an array refers to using the same types of variables within an array. The following arrays are homogenous - const fruits = ['apple', 'orange]; const nums = [0,1,2] const answers= [true, false]; The following arrays are not - const planets = [earth, 3]; const answers = [true, 42]; You may think you have good reasons to include multiple types. For example group together different attributes of earth - ...
It is a commonly recommended practice to cache array lengths while doing for loops and get better performance. Seriously, is that a thing though? Typical for loop In a typical for, you calculate length, iterate and you are done. const arr = new Array(1e7).fill(1); let j = 0; console.time("for-test"); for (let i = 0; i < arr.length; i++) { j += i; } console.timeEnd("for-test"); // 17.850ms 25.295ms 20.860ms Cache for loop Rather than use a typical array length condition, you first find the length and use that variable in all comparisons. This should save time to call the length method each and every time. ...
You don’t have to see assigning values to variables as a chore. There are exciting ways to do those assignments - here are some shorthand ways. Initialize to same value You can initialize variables like so - let i = 0; let j = 0; let k = 0; Or, you can instead do - // prettier-ignore let i = j = k = 0; Initialize variables to different values It is quite common to assign different values during initialization.. let i = 0; let j = 1; let k = 2; .. so why not have a shorthand for that? Just do assignment using the previous way of combining declarations. ...
‘use strict’ is a rather useful statement to have at the beginning of all Javascript modules or functions. It ensures that all code in the module is executed in strict mode. The usage is simple enough. "use strict"; // lot of code You can also enable strict mode to specific functions. function getSum(x, y) { "use strict"; return x + y; } Strict mode has to be at the beginning of files or modules - will not have the desired effect if used anywhere else. ...
It is quite easy to pollute global scope by defining variables or functions that impact core functions. const parseInt = val => console.log("int parsed: ", val); parseInt(1); // int parsed: 1 parseInt has transformed into a printer, thanks to the above code. The practice of “overriding” global scope is not useful and should be avoided like the plague (If you are born in the wrong century - “plague is to be avoided at all costs”). Using such declarations - ...
Map on an array is simple enough - const ran = ["1", "3", "5"].map(val => Number(val)); console.log("ran: ", ran); // ran: [ '1', '3', '5' ] map will specify one element at a time, which is passed to the callback function as val. Let’s say, we ignore the val. const ranToo = ["1", "3", "5"].map(Number); console.log("ranToo: ", ranToo); // [ 1, 3, 5 ] The above code works too. map takes a callback function and runs it on every element, so no problem with the above code. ...