cache.js

function Cache(maxSize) {
  this.data = [];
  this.maxSize = maxSize;
  this.size = 0;

  this.put = function(key, value, ttl) {
  	if(value.length > this.maxSize) {
	  throw new Error('string is too large');
  	}

  	if(this.size + value.length > this.maxSize) {
  		this.lruEvict();
  	}

  	var data = {};
  	data.key = key;
  	data.value = value;
  	data.ttl = setTimeout(() => {
  	  this.remove(key);
  	}, ttl);

  	this.remove();
  	this.data.push(data);
  	this.size += value.length;
  }

  this.remove = function(key) {
  	var index = this.data.findIndex((item) => {
  	  return item.key === key;
  	});

  	if(index !== -1) {
	  clearTimeout(this.data[index].ttl);
  	  this.data[index].ttl = null;
  	  this.size -= this.data[index].value.length;
  	  this.data.splice(index, 1);
  	}
  }

  this.lruEvict = function() {
  	var lastItem = this.data.splice(0, 1);
  	this.size = this.size - lastItem[0].value.length;
  }

  this.get = function(key) {
  	var index = this.data.findIndex((item) => {
  	  return item.key === key;
  	});

  	if(index === -1) {
  	  throw new Error('Key is not present in cache');
  	} else {
  	  var item = this.data.splice(index, 1);
  	  this.data.push(item[0]);
  	}

  	return item[0].value;
  }
}


var obj = new Cache(100);
obj.put('a', 'lorem ipsum dolor sit amet', 10000);
obj.put('b', 'lorem ipsum dolor sit amet', 10000);
obj.put('c', 'lorem ipsum dolor sit amet', 10000);
obj.put('d', 'lorem ipsum dolor sit amet', 10000);
obj.get('b');
obj.get('c');
obj.get('d');

// this will not be available 
obj.get('a');

//After 10 sec, this will not be available
obj.get('c');