js手动实现缓存方法

function memoize(fn) {
  const cache = {};
  return function (param) {
    if (cache[param]) {
      console.log('cached');
      return cache[param];
    } else {
      let result = fn(param);
      cache[param] = result;
      console.log(`not cached`);
      return result;
    }
  }
}

const toUpper = (str ="")=> str.toUpperCase();

const toUpperMemoized = memoize(toUpper);

toUpperMemoized("abcdef");
toUpperMemoized("abcdef");

这个缓存函数适用于接受一个参数。我们需要改变下，让它接受多个参数。

const slice = Array.prototype.slice;
function memoize(fn) {
  const cache = {};
  return (...args) => {
    const params = slice.call(args);
    console.log(params);
    if (cache[params]) {
      console.log('cached');
      return cache[params];
    } else {
      let result = fn(...args);
      cache[params] = result;
      console.log(`not cached`);
      return result;
    }
  }
}
const makeFullName = (fName, lName) => `${fName} ${lName}`;
const reduceAdd = (numbers, startingValue = 0) => numbers.reduce((total, cur) => total + cur, startingValue);

const memoizedMakeFullName = memoize(makeFullName);
const memoizedReduceAdd = memoize(reduceAdd);

memoizedMakeFullName("Marko", "Polo");
memoizedMakeFullName("Marko", "Polo");

memoizedReduceAdd([1, 2, 3, 4, 5], 5);
memoizedReduceAdd([1, 2, 3, 4, 5], 5);