Check.js

class Check {
  constructor(value) {
    this.value = value
    this.result = false
  }

  match(pattern) {
    const patterns = {
      alpha: /^[a-z\s]+$/i,
      alnum: /^[a-z0-9\s]+$/i,
      num: /^[0-9]+$/,
      phone: /^[+]?[(]?[0-9]{3,4}[)]?[-\s.]?[0-9]{3}[-\s.]?[0-9]{1,8}$/im,
      email: /^\w+([\.-]?\w+)*@\w+([\.-]?\w+)*(\.\w{2,3})+$/
    }
    this.result = types.hasOwnProperty(pattern) 
            ? patterns[pattern].test(this.value) 
            : pattern.test(this.value)
    return this
  }

  is(type) {
    const types = {
      string: 'string',
      number: 'number',
      boolean: 'boolean',
      object: 'object',
      array: 'object'
    }
    if (types.hasOwnProperty(type)) {
      this.result = typeof this.value === types[type]
      if (type === 'array') {
        this.result = Array.isArray(this.value)
      } 
    }
    return this
  }

  in(list) {
    if (this.isArray(list)) {
      this.result = list.includes(this.value)
    } else if (typeof list === 'object') {
      this.result = list.hasOwnProperty(this.value)
    }
    return this
  }

  equal(value) {
    if (typeof this.value === 'number') {
      this.result = this.value === value
    } else if (typeof this.value === 'string') {
      this.result = this.value.localeCompare(value) === 0 
    }
    return result
  }

  lower(value) {
    if (typeof this.value === 'number') {
      this.result = this.value < value
    } else if (typeof this.value === 'string') {
      this.result = this.value.length < value
    }
    return this
  }

  greater(value) {
    if (typeof this.value === 'number') {
      this.result = this.value > value
    } else if (typeof this.value === 'string') {
      this.result = this.value.length > value
    }
    return this
  }
}

/* cara pakai */
console.log((new Check(10)).lower(5).result)