Data update

Task/Evolutionary-algorithm/JavaScript/evolutionary-algorithm-2.js

@@ -0,0 +1,125 @@
+"use strict"
+const TARGET = "METHINKS IT IS LIKE A WEASEL";
+const GENE_POOL = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ ';
+const C = 100;
+const MUTATION_RATE = 0.3;
+
+function randomIdGenerator(length) {
+    return Math.floor(Math.random() * length);
+}
+function getGene() {
+    return GENE_POOL[randomIdGenerator(GENE_POOL.length)];
+}
+
+class Parent {
+    _arrayLength;
+    _genePool;
+    _geneGenerator;
+
+    constructor(arrayLength, genePool, geneGenerator) {
+        if (typeof arrayLength === 'number' && arrayLength > 0) {
+            this._arrayLength = arrayLength;
+        }
+
+        if (typeof genePool === 'string' && genePool.length > 0) {
+            this._genePool = [...genePool];
+        }
+
+        if (typeof geneGenerator === 'function') {
+            this._geneGenerator = geneGenerator;
+        }
+    }
+    generate() {
+        const letters = [];
+
+        while (letters.length < this._arrayLength) {
+            letters.push(this._geneGenerator());
+        }
+
+        return letters.join('');
+    }
+}
+
+function fitness(needle, target) {
+    if (needle.length !== target.length) return 0;
+
+    const needleArray = [...needle];
+    let count = 0;
+
+    [...target].forEach((item, index) => {
+        if (item === needleArray[index]) count++;
+    });
+
+    return count;
+}
+
+function mutate({ source, mutationRate }) {
+    if (typeof source !== 'string' || source.length === 0) return '';
+    const sourceLength = source.length;
+    const iterations = Math.floor(sourceLength * mutationRate);
+    const stringArray = [...source];
+
+    for(let i = 0; i < iterations; i++) {
+        const shouldReplace = Boolean(Math.floor(Math.random() * 2));
+
+        if(shouldReplace) {
+            const id = randomIdGenerator(sourceLength);
+            stringArray[id] = getGene();
+        }
+    }
+
+    return stringArray.join('');
+}
+
+function createMutants(parent, mutantNumber) {
+    const mutantArray = [];
+
+    for (let i = 0; i < mutantNumber; i++) {
+        const mutant = mutate({source: parent, mutationRate: MUTATION_RATE});
+
+        mutantArray.push(
+            {
+                mutant,
+                fitness: fitness(mutant, TARGET),
+            },
+        );
+    }
+
+    return mutantArray;
+}
+
+function helperInit(parentString, parentFitness) {
+    const mutant = createMutants(parentString, C)
+        .sort( (a,b) => a.fitness - b.fitness ).pop();
+
+    if (mutant.fitness >= parentFitness) {
+        return {
+            string: mutant.mutant,
+            fitness: mutant.fitness,
+        };
+    }
+
+    return {
+        string: parentString,
+        fitness: parentFitness,
+    };
+}
+
+function run() {
+    const parent = new Parent(TARGET.length, GENE_POOL, getGene);
+    let parentString = parent.generate();
+    let parentFitness = fitness(parentString, TARGET);
+    let genCount = 0;
+
+    while(parentString !== TARGET) {
+        const init = helperInit(parentString, parentFitness);
+        parentString = init.string;
+        parentFitness = init.fitness;
+        console.log(init.string);
+        genCount++;
+    }
+
+    console.log(`Ended in ${genCount} generations`);
+}
+
+run();