This is the code for Modless Tier Shift

formats.js

{
		name: "Tier Shift",
		onBegin: function () {
			let allPokemon = this.p1.pokemon.concat(this.p2.pokemon);
			let boosts = {
				'UU': 5,
				'BL2': 5,
				'RU': 10,
				'BL3': 10,
				'NU': 15,
				'BL4': 15,
				'PU': 20,
				'NFE': 20,
				'LC Uber': 20,
				'LC': 20,
			};
			for (let i = 0, len = allPokemon.length; i < len; i++) {
				let pokemon = allPokemon[i];
				let template = pokemon.baseTemplate;
				let tier = template.tier;
				if (pokemon.set.item) {
					let item = this.getItem(pokemon.set.item);
					if (item.megaEvolves === template.species) tier = this.getTemplate(item.megaStone).tier;
				}
				if (tier.charAt(0) === '(') tier = tier.slice(1, -1);
				let boost = (tier in boosts) ? boosts[tier] : 0;
				let baseStats = {};
				for (let statName in template.baseStats) {
					baseStats[statName] = this.clampIntRange(template.baseStats[statName] + boost, 1, 255);
				}
				pokemon.hp = pokemon.maxhp = Math.floor(Math.floor(2 * template.baseStats['hp'] + pokemon.set.ivs['hp'] + Math.floor(pokemon.set.evs['hp'] >> 2) + 100) * pokemon.level / 100 + 10);
				pokemon.template = template;
				pokemon.formeChange(template);
			}
		},
		ruleset: ['OU'],
	},