True or false? What appears in the console?
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JavaScript uses the double-precision floating-point numbers even to represent integers. This means that the biggest number that can be stored safely as a JS number is 2^53^ - 1 or 9007199254740991. This value is stored as a static constant Math.MAX_SAFE_INTEGER
.
console.log(Math.MAX_SAFE_INTEGER); // 9007199254740991
console.log(Math.pow(2, 53) - 1); // 9007199254740991
Having the value Math.MAX_SAFE_INTEGER
doesn’t mean that it’s impossible to have a bigger number in JS. But, when we continue to increase the number, the loss of precision occurs.
console.log(Number.MAX_SAFE_INTEGER + 1); // 9007199254740992
console.log(Number.MAX_SAFE_INTEGER + 2); // 9007199254740992
As you see, by adding 1 and then 2 to Number.MAX_SAFE_INTEGER
, we got the same number.
If you’re building an application where such behavior is critical, then you should use BigInt
instead of the regular JavaScript Number
.
ANSWER: There will be a loss of precision due to rounding and safe integer overflow. Both x
and y
will equal 9007199254740992
. The message true
will be printed to the console.
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Top comments (1)
Why
Number.MAX_SAFE_INTEGER + 2 !== Number.MAX_SAFE_INTEGER + 3
?