O(cetija)

Benchmark created on

Description

https://stackoverflow.com/questions/55651936/why-i-cant-use-string-charcodeat-at-elements-of-reduce-callback/55651977#55651977

Convolution of the user's nickname into one of the default avatars filename.

For Habr with ❤️

Setup

(function(){"use strict";
	
var U = 0; // un_eliminate
var k = 0;

var users = [
	{
		id: 0,
		alias: "User_Nick_Name_00"
	},{
		id: 1,
		alias: "User_01"
	}
];

function generateDefAvatarNum(alias){
	var sum = 0;
	var len = alias.length;

	for(var i = 0; i < len; i++){
		sum += alias.charCodeAt(i);  // `charCodeAt(i)` faster with i++, slower with i--
	}

	return (""+(Math.abs(sum%200)+1)).padStart(3,"0");
};

var getDefAvatarFileNum = (function(){
	var respondentId = users[1].id;
	
	// cache
	var respondentDefAvatarNum = "",
		myDefAvatarNum = "";
	// or `["",""]` - code below is faster than with `new Array(2)` or `[,,]`
	
	
	return function(author){
		var id = author.id;

		var defAvatarNum = (id === respondentId ? respondentDefAvatarNum : myDefAvatarNum);
		if(!defAvatarNum){
			defAvatarNum = generateDefAvatarNum(author.alias);

			if(id === respondentId) respondentDefAvatarNum = defAvatarNum;
			else                    myDefAvatarNum         = defAvatarNum;
		}

		return defAvatarNum;
	};
})();

Teardown

window.__un_eliminate__ = U;

})();  // (function(){"use strict";

Test runner

Ready to run.

Testing in
TestOps/sec
Original: .split().reduce() → charCodeAt(0)
U |= ( 
	(Math.abs(
		users[k].alias
		.split("")
		.reduce((sum,char)=>sum+char.charCodeAt(0), 0)
	%200)+1).toString().padStart(3,"0") 
).length;

k ^= 1;
ready
for … of → charCodeAt(0)
var sum = 0;

for(const char of users[k].alias) {
	sum += char.charCodeAt(0);
}

U |= ( (""+(Math.abs(sum%200)+1)).padStart(3,"0") ).length;

k ^= 1;
ready
for → charCodeAt(i)
var alias = users[k].alias;
var sum = 0;
var len = alias.length;

for(var i = 0; i < len; i++){
	sum += alias.charCodeAt(i);
}

U |= ( (""+(Math.abs(sum%200)+1)).padStart(3,"0") ).length;

k ^= 1;
ready
Cache: for → charCodeAt(i)
U |= ( getDefAvatarFileNum(users[k]) ).length;

k ^= 1;
ready

Revisions

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