JavaScript Fun Question: Factoring Prime Factors

The process of decomposing a positive integer into several prime factors is called decomposing prime factors.

A simple example:

The decomposed prime factor of 24 is 2*2*2*3, which is abbreviated as (2^3) * (3^1).

In terms of computers, we can use a hash table to store this result, which can be expressed in the following form in JS:

{ '2': 3, '3': 1 }

So, how to decompose prime factors?

First of all, you need a method to determine whether it is a prime number.

function isPrime(n){ for(var i=2;i<=Math.sqrt(n);i++){ if(n % i == 0){ return false; } } return true; }

Then, use short division to decompose.

function PrimeFactorizer(n){ //用来存储结果的hash var hash = {}; while(n > 1){ //从最小的质数开始除 for(var i=2;i<=n;i++){ if(isPrime(i) && n % i == 0){ //如果hash中有这个质数，则存储的数目+1 if(hash[i]){ hash[i] = hash[i] + 1; }//否则把该质数作为key，value为1 else{ hash[i] = 1; } //除掉这个最小的质数因子 n /= i; } } } //给实例上加个factor属性 this.factor = hash; hash = null; } new PrimeFactorizer(24).factor // { '2': 3, '3': 1 }

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