![]() ![]() Now, let's have a look at some strict equality operator examples: > true = true Meaning the output won't be true unless both the type and values of the two expressions match. This means that, unlike the loose equality operator we talked about before, there is no implicit conversion. Triple equals in JavaScript stands for strict equality. While these would all be false: > undefined = false įalse Strict Equality Operator in JavaScript (=) So, these would all be true: > false = 0 NaN compared to anything (even another NaN) returns false.undefined and null return true when compared to themselves or each other, and false when compared to anything else.There are a couple of simple rules when it comes to using the double equals operator on falsy values: In JavaScript, there are seven falsy values - false, 0, "",, null, undefined, NaN. Falsy Value Comparison in JavaScriptĪ falsy value is a variable which evaluates to false. That's obviously = to 2, so the expression returns true. This side of the expression therefore also evaluated to true + true, which is implicitly converted into 1+1. The + operator, which in this case is a string.ĭownload the eBook > ( "42" = '42') + (42 = "42") = 2 To sum up, the JavaScript engine tries to convert both values to a type that supports Finally, the result is returned and assigned to x. However, we can also concatenate strings with +, so let's match them as strings and perform concatenation. However, there's an empty string, "", there. ![]() This implies integer addition with the next number. The first number is 1 and has + operator besides it. The expression should be evaluated and assigned to x. To explain this example, let's look at it from a JavaScript engine's perspective: This coercion type is usually done when we use operators on different types, but can be reasonably "matched" by one of them, for example: // x is going to be cast to the string "1". Implicit type coercion is, on the other hand, done implicitly by JavaScript. Similarly,this would result in y being cast to the boolean value false let y = Boolean( 0) Type coercion can be explicit and implicit.Įxplicit type coercion is, as its name implies, done explicitly in code by a programmer, using the built-in methods that JavaScript provides ( Number(), String(), Boolean().).įor example: // This would result in x being a number 42 let x = Number( "42") The process of converting a value from one type to another is called type coercion. Meaning that the expressions don't necessarily need to be of the same type. This permits the JavaScript engine to try and cast these expressions to a common type. Loose Equality Operator in JavaScript (=)ĭouble equals in JavaScript are testing for loose equality. In this article, we will explain the differences between loose and strict equality operators and go over some examples of their usage. JavaScript is interesting because it's got two visually very similar, but in practice very different comparison operators for equality: = and =. != and != - not equal to (loose and strict inequality operator).= and = - equal to (loose and strict equality operator).If the two variables or objects are deduced to be equal the operator returns true, and false if they aren't. Comparison operators are used in logical statements to determine whether two variables or objects are equal by some already set or custom defined criteria.
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