update: added BloomFilters

Author: ashokdey

src/_DataStructures_/BloomFilters/index.js

@@ -0,0 +1,97 @@
+class BloomFilters {
+  constructor(size = 101) {
+    this.size = size;
+    this.data = this.getStorage(size);
+  }
+
+  add(element) {
+    const indices = this.getIndices(element);
+
+    for (let i = 0; i < indices.length; i += 1) {
+      this.data.setBit(indices[i]);
+    }
+  }
+
+  contains(element) {
+    const indices = this.getIndices(element);
+
+    for (let i = 0; i < indices.length; i += 1) {
+      const index = indices[i];
+      if (!this.data.getBit(index)) {
+        return false; // item is definately not there
+      }
+    }
+    return true; // item may be there
+  }
+
+  getIndices(element) {
+    return [this.hashOne(element), this.hashTwo(element), this.hashThree(element)];
+  }
+
+  hashOne(value) {
+    const stringValue = String(value);
+    let hashVal = 0;
+
+    for (let i = 0; i < stringValue.length; i += 1) {
+      hashVal += stringValue.charCodeAt(i) - 96;
+    }
+
+    // eslint-disable-next-line no-bitwise
+    hashVal &= hashVal;
+
+    return Math.abs(hashVal % this.size);
+  }
+
+  hashTwo(value) {
+    const stringValue = String(value);
+    const PRIME_MULTIPLIER = 1801; // Random prime number
+    let hashVal = 0;
+
+    for (let i = 0; i < stringValue.length; i += 1) {
+      hashVal += stringValue.charCodeAt(i) - 96;
+      hashVal *= PRIME_MULTIPLIER;
+    }
+
+    return Math.abs(hashVal % this.size);
+  }
+
+  hashThree(value) {
+    const stringValue = String(value);
+    const PRIME_MULTIPLIER = 1801; // Random prime number
+    const PRIME_ADDER = 2029; // Random prime number
+    let hashVal = 0;
+
+    for (let i = 0; i < stringValue.length; i += 1) {
+      hashVal += stringValue.charCodeAt(i) - 96;
+      hashVal *= PRIME_MULTIPLIER;
+      hashVal += PRIME_ADDER;
+    }
+    // eslint-disable-next-line no-bitwise
+    hashVal &= hashVal;
+    return Math.abs(hashVal % this.size);
+  }
+
+  // eslint-disable-next-line class-methods-use-this
+  getStorage(size) {
+    const data = new Array(size).fill(0);
+
+    return {
+      setBit(index) {
+        data[index] = 1;
+      },
+      getBit(index) {
+        return data[index];
+      },
+    };
+  }
+}
+
+// const b = new BloomFilters();
+
+// b.add('React.js');
+// b.add('Node.js');
+
+// console.log(b.contains('JavaScript'));
+// console.log(b.contains('React.js'));
+
+module.exports = BloomFilters;