实现一个 jQuery 的 API

window.jQuery = ???
window.$ = jQuery

var $div = $('div')
$div.addClass('red') // 可将所有 div 的 class 添加一个 red
$div.setText('hi') // 可将所有 div 的 textContent 变为 hi

1.首先接收一个node或选择器
先声明一个变量nodes，然后对接收的nodeOrSelector做一下类型检测，如果是字符串，就去找到对应的nodes伪数组；如果是单个节点，则返回伪数组

let nodes = {}
  if (typeof nodeOrSelector === 'string') {
    let temp = document.querySelectorAll(nodeOrSelector)
    for (let i = 0; i < temp.length; i++) {
      nodes[i] = temp[i]
    }
    nodes.length = temp.length
  } else if (nodeOrSelector instanceof Node) {
    nodes = {
      0: nodeOrSelector,
      length: 1
    }
  }

2.封装成一个伪数组

window.jQuery = function(nodeOrSelector) {
  let nodes = {}
  if (typeof nodeOrSelector === 'string') {
    let temp = document.querySelectorAll(nodeOrSelector)
    for (let i = 0; i < temp.length; i++) {
      nodes[i] = temp[i]
    }
    nodes.length = temp.length
  } else if (nodeOrSelector instanceof Node) {
    nodes = {
      0: nodeOrSelector,
      length: 1
    }
  }
}

3.在伪数组中添加需要的API

nodes.addClass = function(classes) {
  classes.forEach((value) => {
    for (let i = 0; i < nodes.length; i++ ) {
      nodes[i].classList.add(value)
    }
  })
}
nodes.setText = function(text) {
  for (let i = 0; i < nodes.length; i++ ){
    nodes[i].textContent = text
  }
}

4.送出伪数组

window.jQuery = function(nodeOrSelector) {
  let nodes = {}
  if (typeof nodeOrSelector === 'string') {
    let temp = document.querySelectorAll(nodeOrSelector)
    for (let i = 0; i < temp.length; i++) {
      nodes[i] = temp[i]
    }
    nodes.length = temp.length
  } else if (nodeOrSelector instanceof Node) {
    nodes = {
      0: nodeOrSelector,
      length: 1
    }
  }
  nodes.addClass = function(classes) {
    classes.forEach((value) => {
      for (let i = 0; i < nodes.length; i++ ) {
        nodes[i].classList.add(value)
      }
    })
  }
  nodes.setText = function(text) {
    for (let i = 0; i < nodes.length; i++ ){
      nodes[i].textContent = text
    }
  }
  return nodes
}

window.$ = jQuery
var $div = $('div')
$div.addClass(['red'])
$div.setText('hi')