Question

How to calculate the largest positive integer in a 64-bit system in JavaScript

Answer 1

/**
 * Returns the largest positive value that can be stored
 * in a signed 64-bit integer.
 *
 * A signed 64-bit integer uses:
 * - 1 bit for the sign
 * - 63 bits for the value
 *
 * Maximum value = 2^63 - 1
 *
 * @returns {bigint}
 */
function getMaxInt64() {
    return (1n << 63n) - 1n;
}

// Example usage
const maxValue = getMaxInt64();

console.log(`Maximum Int64 value: ${maxValue}`);



/*
run:

Maximum Int64 value: 9223372036854775807
  
*/

 

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Answer 2

const MAX_INT64 = (1n << 63n) - 1n;

console.log(`Maximum Int64 value: ${MAX_INT64}`);



/*
run:

Maximum Int64 value: 9223372036854775807
  
*/

 

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Answer 3

/**
 * Returns the maximum value for a signed integer
 * of the specified bit width.
 *
 * @param {number} bits
 * @returns {bigint}
 */
function getMaxSignedInteger(bits) {
    return (1n << BigInt(bits - 1)) - 1n;
}

// Example
console.log(getMaxSignedInteger(64)); // 9223372036854775807n



/*
run:

9223372036854775807n
  
*/

 

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