text: // 高阶函数-函数作为参数
  
  function forEach (array, fn) {
    for (let i = 0; i < array.length; i++) {
      fn(array[i])
    }
  }
  
  // 测试
  // let arr = [1, 3, 4, 7, 8]
  
  // forEach(arr, function (item) {
  //   console.log(item)
  // })
  
  
  // filter
  function filter (array, fn) {
    let results = []
    for (let i = 0; i < array.length; i++) {
      if (fn(array[i])) {
        results.push(array[i])
      }
    }
    return results
  }
  
  // 测试
  let arr = [1, 3, 4, 7, 8]
  let r = filter(arr, function (item) {
    return item % 2 === 0
  })
  
  console.log(r)