Along with some practical examples Before we begin our JS Coercion exploration it’s worthy to note that this post exists because JS is an (maybe weakly-typed based upon your definition). untyped language Typed Language A strongly- programming is one in which each of data (such as integer, character, hexadecimal, packed decimal, and so forth) is predefined as part of the programming and all constants or variables defined for a given program must be described with one of the data types. typed language type language — source yo What this means for us as JS users is that the language may be forced to make certain Type decisions at compile time. In this post we will refer to 2 different types of coercion, and . rule based Explicit Implicit Explicit coercion is an obvious attempt from the author to convert a value of one type to another type. Implicit coercion occurs as a less-obvious side effect of another operation. See the below examples( ): gist implicit/explicit coercion Note that in the example above that both approaches, implicit and explicit, result in the same outcome, it is the that is interesting and results in some debate. Namely readability being the point of contention. Almost always, someone other than you is going to be reading your code. Which of the above methods is more readable? how With all that being said, let’s take a look at how JS handles comparisons between data types using and , and also when using and . == === null undefined null vs. undefined Here are some code examples, explained in more detail below( ): gist null vs undefined types The main takeaways from the code above are: is an null Object is it’s own distinct type undefined undefined Comparisons We are going to take a look now at the results of comparing values of different types using both the Equality [==](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Comparison_Operators) and Strict Equality [===](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Comparison_Operators) comparisons. OK, let’s force the JS interpreter to make some guesses as to our intentions: undefined/null Note that and equal each other with the Equality Comparison(4–5) but not with the Strict Equality Comparison(8–9) undefined null Let’s look at some , , and comparisons: String Number Boolean string/number/bool By now you may notice a pattern. When comparing vals of different types using the Equality comparison, JS will likely correctly coerce the values. Accuracy though is achieved through the Strict comparison. Conclusion In the end coercion is a necessary evil of untyped languages. My suggestion is: As you are writing code use the Strict Comparison unless you can justify not doing so. ALWAYS _One of the most anticipated new features in the ES6 Javascript standard was the Arrow Function Expression. It promises…_medium.com Javascript ES6 — Arrow Functions and Lexical `this` As always, let us know your thoughts and questions and follow us on . Keep after it. PLEASE twitter If this post was helpful, please click the clap 👏button below a few times to show your support! ⬇⬇

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Javascript Coercion Explained

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Ben Garrison

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