linear_search.js

class Search {
  constructor(input) {
    this.input = input
  }

  linearSearch(target) {
    const array = this.input

    const len = array.length

    for (let i = 0; i < len; i++) {
      if (array[i] === target) {
        return 'Element present in index ' + i
      }
    }

    return 'Element not found'
  }
}

var search = new Search([1, 2, 3, 4, 5, 6])
search.linearSearch(3) // Element present in index 2
search.linearSearch(30) // Element not found