Bloom filter implementation in JavaScript

// Bloom filter implementation in JavaScript

class BloomFilter {
  constructor(size) {
    this.array = new Array(size).fill(0);
    this.indexes = [];
  }

  hash(string) {
    let hash = 0;
    for (let i = 0; i < string.length; i++) {
      const char = string.charCodeAt(i);
      hash = (hash << 5) - hash + char;
      hash &= hash;
    }
    return hash;
  }

  getIndexes(string) {
    const hash1 = Math.abs(this.hash(string)) % this.array.length;
    const hash2 = Math.abs(this.hash(string + '1')) % this.array.length;
    return [hash1, hash2];
  }

  add(string) {
    this.indexes = this.getIndexes(string);
    for (let i = 0; i < this.indexes.length; i++) {
      const index = this.indexes[i];
      this.array[index] = 1;
    }
  }

  contains(string) {
    this.indexes = this.getIndexes(string);
    for (let i = 0; i < this.indexes.length; i++) {
      const index = this.indexes[i];
      if (this.array[index] === 0) {
        return false;
      }
    }
    return true;
  }

  export() {
    return this.array;
  }

  import(array) {
    if (array.length !== this.array.length) {
      throw 'Cannot import array of different size';
    }
    this.array = array;
  }
}

module.exports = BloomFilter;