And its typeof should return With well-known symbols, there's a way to get rid of type coercion. For any floating point architecture, there is a number that represents the smallest interval between distinguishable numbers. site design / logo © 2020 Stack Exchange Inc; user contributions licensed under Javascript/jQuery gives weird result from addition. This seems like it would be very problematic. Some of them can quickly turn our everyday job into hell, and some of them can make us laugh out loud.The primary goal of this list is to collect some crazy examples and explain how they work, if possible. At this scale, it rounds to the nearest even number. It is called EPSILON.It will be a part of the EcmaScript standard in the near future. Here's the original one:The specification strictly defines the logic behind this behavior:Four mutually exclusive relations are possible: less than, equal, greater than, and unordered. They are kind of interesting:Consider this example of a generator which yields itself:As you can see, the returned value is an object with its To understand why this works that way, read these sections of the specification:It seems like we're declaring a class inside of class. If you execute 0.1 it will say 0.1 due to the fact that javascript has a default precision size to show you which is the length of your input OR 1 if it's over 18. What the value of Interesting examples could be composed with spreading of arrays. By clicking “Post Your Answer”, you agree to our To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Should be an error, however, we get the string And ES6 standardized shorthand method definitions. It can convert string representations of integers and floats, as well as the non-string values When you're performing addition or multiplication, the That's why we can add boolean values as regular numbers and get correct results.Impressed? I find a useful equality test and put it here:

Step-by-step, it looks like this:You've created an array with 4 empty elements. Explanation: The abstract equality operator converts both sides to numbers to compare them, and both sides become the number 0 for different reasons.

Use Git or checkout with SVN using the web URL. The issue is that the first subject of addition isn't actually just 0.1, it's actually 0.100000000000000005551 same with 0.2, it's actually value is 0.200000000000000011102. Stack Overflow works best with JavaScript enabled Every NaN shall compare unordered with everything, including itself.By breaking that mass of symbols into pieces, we notice that the following pattern occurs often:Thinking of a string as an array we can access its first character via An array is a truthy value, however, it's not equal to Here are links to the corresponding sections in the ECMA-262 specification:The explanation is the same as for previous example. Consider these examples:What's happening in the first four examples? It Another relevant answer with some examples of how to handle the calculations:This will reduce the precision of float numbers but solves the problem if you are not working with very small values.

In this case, as the operator precedence is the same, and the evaluation is from left to right, you end up with (""+1+10+2) using + 's implicit tostring conversion for string concatenation, or the string "1102". However, if we try to get a value of This happens because when something doesn't have a prototype, it will be wrapped into a wrapper object using the Then we've passed this object to the template literal, so the The example above is a great task for an interview.

Here's the corresponding link:This is not a part of the specification. Moreover, they're a part of the specification:However, you can check the type of an object by using the This is caused by IEEE 754-2008 standard for Binary Floating-Point Arithmetic. The problem is that 1/10 cannot be accurately represented as a binary fraction just like 1/3 cannot be represented as a decimal fraction.The workarounds include rounding to only the number of decimal places that you need and either work with strings, which are accurate:Or you can use cents instead of dollars when counting money:That way you only work with integers and you don't have to worry about decimal and binary fractions at all.The situation of representing numbers in JavaScript may be a little bit more complicated than it used to. Here's how it works:Read more about Relational operators in the specification:Often the results of arithmetic operations in JavaScript might be quite unexpected. Consider this:Obviously, we can spread and wrap the elements of an array as many times as we want:Not many programmers know about labels in JavaScript. Read more:This problem is so known that there is even a website called You can add your own methods to wrapper objects like Why does this work that way? Take a look:Arrow functions cannot be used as constructors and will throw an error when used with new.