JavaScript

As with many other things in JavaScript Automatic Semicolon Insertion is usually not a problem but it can occasionally bite you if you are unaware of it. What Automatic Semicolon Insertion does is really simple. It basically boils down to semicolons being optional in JavaScript and the parser  injecting them when it is appropriate. That might sound very nice, after all you can leave semicolons out and the right thing will happen. For example the following code, without a single semicolon, is completely valid and will print a sum of 3 as expected: 1: console.log(add(1, 2)) 2: 3: function add(x, … Continue reading X things every JavaScript developer should know: Automatic Semicolon Insertion

Another item of things every JavaScript developer should know is how comparisons work. Just like with some of the other JavaScript, or I should really say ECMAScript, features anything you know about C# or Java could actually be misleading here.   To == or to === One of the weird things is there are actually two comparison operators in JavaScript, the double and the triple equals. The == is called the equals operator, see section 11.9.1 of the ECMAScript standard, and was the original equality operator. Unfortunately the way this operator works is quite some cause for confusion and as … Continue reading X things every JavaScript developer should know: Comparisons

One thing that developers often confuses with JavaScript is Boolean logic. It seems to simple, you use for example an if statement and put a boolean expression in there and if it is true the block of code is executed other wise the else block is executed. Something like this: 1: (function () { 2: var data = []; 3:  4: if (data.length > 0) { 5: console.log("The data array is not empty"); 6: } else { 7: console.log("The data array is empty"); 8: } 9: }());   And if you run it it will do exactly what you would … Continue reading X things every JavaScript developer should know: Truthy and falsy

In the previous blog post I explained that you should normally use an Immediately-Invoked Function Expression (IIFE) to give variables function scope. That works fine as log as we remember to declare our variables using the var keyword. However when we forget the var keyword we are back to the original problem as the variables are added to the global scope.   Leaking undeclared variables As you can see in the two code snippets below the text variables are not declared using var. Even though they are only used inside a function they are still added to the global scope. … Continue reading X things every JavaScript developer should know: use strict

I see a lot of developer with a C# or Java background adopting JavaScript as well these days. Not that it should be a big surprise, lots of business applications are developed as client side browser based applications these days. And like it or not JavaScript is the language of the browser. Unfortunately the JavaScript syntax resembles that of Java or C# resulting in these developers thinking that they can easily master the language. And even though JavaScript is not a hard language to master there are some important differences and gotchas everyone needs to be aware of. So on … Continue reading X things every JavaScript developer should know: scoping