In JavaScript, what does the === operator check?
AnswerEquality of value and type, without type conversion
Strict equality (===) returns true only if both operands have the same type and value; == may convert types first.
Coding · Facts & stats
JS facts & stats
7 fact-checked facts about JavaScript, each with the reason behind it. 5 more are in today's round and join this page after it closes.
The basics
What does [1, 2, 3].length evaluate to in JavaScript?
Answer3
An array's length property gives the number of elements, here three.
Going deeper
In JavaScript, what is the result of "5" + 3?
Answer"53"
When one operand of + is a string, JavaScript converts the other to a string and joins them.
What is the name of the language standard that JavaScript implements?
AnswerECMAScript
JavaScript is standardised by Ecma International as ECMAScript, specified in ECMA-262.
What happens if you try to reassign a variable declared with const?
AnswerA TypeError is thrown
const creates a binding that cannot be reassigned; attempting it throws a TypeError.
Expert level
In JavaScript, what does NaN === NaN evaluate to?
Answerfalse
NaN is the only value not equal to itself; use Number.isNaN() to test for it.
What is the value of Number.MAX_SAFE_INTEGER in JavaScript?
Answer2^53 - 1
JavaScript numbers are 64-bit floats, which represent every integer exactly only up to 2^53 - 1.
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