5种最流行的发送HTTP请求的方法

//create XMLHttpRequest object
const xhr = new XMLHttpRequest()
//open a get request with the remote server URL
xhr.open("GET", "https://world.openfoodfacts.org/category/pastas/1.json")
//send the Http request
xhr.send()
//EVENT HANDLERS
//triggered when the response is completed
xhr.onload = function() {
  if (xhr.status === 200) {
    //parse JSON datax`x
    data = JSON.parse(xhr.responseText)
    console.log(data.count)
    console.log(data.products)
  } else if (xhr.status === 404) {
    console.log("No records found")
  }
}
//triggered when a network-level error occurs with the request
xhr.onerror = function() {
  console.log("Network error occurred")
}
//triggered periodically as the client receives data
//used to monitor the progress of the request
xhr.onprogress = function(e) {
  if (e.lengthComputable) {
    console.log(`${e.loaded} B of ${e.total} B loaded!`)
  } else {
    console.log(`${e.loaded} B loaded!`)
  }
}

// create XMLHttpRequest object
const xhr = new XMLHttpRequest()
// open a POST request
xhr.open("POST", "/food")
// set content-type header to JSON
xhr.setRequestHeader("Content-Type", "application/json");
// send JSON data to the remote server
xhr.send(JSON.stringify(food))
// Event Handlers
// track data upload progress
xhr.upload.onprogress = function(e) {
  console.log(`${e.loaded}B of ${e.total}B uploaded!`)
}
// triggered when data upload is finished
xhr.upload.onload = function(e) {
  console.log("Upload completed")
}
// triggered when the response is fully received
xhr.onload = function() {
  console.log(xhr.status)
}
// triggered due to a network-level error
xhr.onerror = function() {
  console.log("Network error occurred")
}