filter ( Boolean ) // Filter out falsy values and log remaining truthy values console. 'false' (a string containing the text “false”)Ī single value can therefore be used within conditions.'0' (a string containing a single zero).Understanding the concepts and their effect on comparison helps when debugging JavaScript applications.Įverything else is truthy. Some of the rules that determine how non-Boolean values are translated into true or false values are a little bizarre. What is Map The Map object holds key-value pairs and remembers the.
Symbol (a unique and immutable primitive new to ES6/2015)Įverything else is an Object - including arrays.Īs well as a type, each value also has an inherent Boolean value, generally known as either truthy or falsy. Map object in javascript not equal to array.map. insert a special symbol into an MS Office application (e.g., Word) or a website using HTML, CSS, or JavaScript.SameValueZero: used by TypedArray and ArrayBuffer constructors, as well as Map and Set operations, and also String.prototype. BigInt (an integer value larger than 2^53 – 1) There are four equality algorithms in JavaScript: IsLooselyEqual ( ) IsStrictlyEqual ( ): used by, , and case -matching.Number (this includes Infinity and NaN - not a number!).Undefined (a variable with no defined value).
Internally, JavaScript sets a value to one of seven primitive data types:
Note that due to using 32-bit representation for numbers both -967295 (2 32 - 1) results in 0. Bitwise NOTing any number x yields - (x + 1). That is, the presence of the most significant bit is used to express negative integers. Seemingly different values equate to true when compared with = (loose or abstract equality) because JavaScript (effectively) converts each to a string representation before comparison: // all true 1 = '1' 1 = '1' = Ī more obvious false result occurs when comparing with = (strict equality) because the type is considered: // all false 1 = '1' 1 = '1' = The 32-bit signed integer operand is inverted according to two's complement. JavaScript variables are loosely/dynamically typed and the language doesn’t care how a value is declared or changed: let x
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