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 // { &#39;2&#39;: 3, &#39;3&#39;: 1 }

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