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diff --git a/docs/performance/memory/monster_example.md b/docs/performance/memory/monster_example.md new file mode 100644 index 0000000000..d351803a8d --- /dev/null +++ b/docs/performance/memory/monster_example.md @@ -0,0 +1,79 @@ +# Monster example slug + +This article describes a very simple web page that we'll use to +illustrate some features of the Memory tool. + +You can try the site at +<https://mdn.github.io/performance-scenarios/js-allocs/alloc.html>. +Heres the code: + +```js +var MONSTER_COUNT = 5000; +var MIN_NAME_LENGTH = 2; +var MAX_NAME_LENGTH = 48; + +function Monster() { + + function randomInt(min, max) { + return Math.floor(Math.random() * (max - min + 1)) + min; + } + + function randomName() { + var chars = "abcdefghijklmnopqrstuvwxyz"; + var nameLength = randomInt(MIN_NAME_LENGTH, MAX_NAME_LENGTH); + var name = ""; + for (var j = 0; j < nameLength; j++) { + name += chars[randomInt(0, chars.length-1)]; + } + return name; + } + + this.name = randomName(); + this.eyeCount = randomInt(0, 25); + this.tentacleCount = randomInt(0, 250); +} + +function makeMonsters() { + var monsters = { + "friendly": [], + "fierce": [], + "undecided": [] + }; + + for (var i = 0; i < MONSTER_COUNT; i++) { + monsters.friendly.push(new Monster()); + } + + for (var i = 0; i < MONSTER_COUNT; i++) { + monsters.fierce.push(new Monster()); + } + + for (var i = 0; i < MONSTER_COUNT; i++) { + monsters.undecided.push(new Monster()); + } + + console.log(monsters); +} + +var makeMonstersButton = document.getElementById("make-monsters"); +makeMonstersButton.addEventListener("click", makeMonsters); +``` + +The page contains a button: when you push the button, the code creates +some monsters. Specifically: + +- the code creates an object with three properties, each an array: + - one for fierce monsters + - one for friendly monsters + - one for monsters who haven't decided yet. +- for each array, the code creates and appends 5000 + randomly-initialized monsters. Each monster has: + - a string, for the monster's name + - a number representing the number of eyes it has + - a number representing the number of tentacles it has. + +So the structure of the memory allocated on the JavaScript heap is an +object containing three arrays, each containing 5000 objects (monsters), +each object containing a string and two integers: + +[![](../img/monsters.svg)] |