How can I memoize a JavaScript function that accepts multiple arguments, including objects?

Question

I’m trying to improve the performance of a computationally expensive JavaScript function by memoizing it. The function accepts multiple arguments, including objects. Here's an example:

function expensiveCalculation(a, b, options) {
    // Simulating an expensive operation
    return a + b + options.value;
}

const options = { value: 10 };
console.log(expensiveCalculation(5, 3, options)); // 18
console.log(expensiveCalculation(5, 3, options)); // Should use the cached result

memoizedCalculation(5, 3, options);

Is it reasonable to hash the args to use as a caching key? Or are there like huge buffers and stuff in your args? — Brad
– Brad, Commented Nov 28, 2024 at 18:34
What exactly is the problem? Do you know how to memoise a function in general? — Bergi
– Bergi, Commented Nov 29, 2024 at 3:01

Carsten Massmann · Accepted Answer · 2024-11-29 03:45:24Z

0

Memoizing can be done in many different ways. A typical approach of doing it would be to define a function in a scope together with a map (here: cache) that acts as a static memory for any previously calculated results:

const fn = (()=>{
 let res;
 const cache=new Map();
 return function(a,b,options) {
   const key=`${a},${b},${options.value}`;
  // Simulating an expensive operation
  res=cache.get(key);
  if(res===undefined) {
   console.log("calculating");
   // the lengthy computation:
   res=a+b+options.value
   cache.set(key,res);
  }
  return res;
 }
})();

// Now, run some tests:
console.log([fn(2,3,{value:4}),
fn(2,3,{arr:[1,2,3],value:4}),
fn(2,3,{value:4,name:"new"})]);

answered Nov 29, 2024 at 3:45

Carsten Massmann

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