问题

I would like to use a javascript loop to create multiple HTML wrapper elements and insert JSON response API data into some of the elements (image, title, url, etc...).

Is this something I need to go line-by-line with?

<a class="scoreboard-video-outer-link" href="">
  <div class="scoreboard-video--wrapper">
    <div class="scoreboard-video--thumbnail">
      <img src="http://via.placeholder.com/350x150">
    </div>
    <div class="scoreboard-video--info">
      <div class="scoreboard-video--title">Pelicans @ Bulls Postgame: E'Twaun Moore 10-8-17</div>
    </div>
  </div>
</a>

What I am trying:

var link = document.createElement('a');
document.getElementsByTagName("a")[0].setAttribute("class", "scoreboard-video-outer-link");
document.getElementsByTagName("a")[0].setAttribute("url", "google.com"); 
mainWrapper.appendChild(link);

var videoWrapper= document.createElement('div');
document.getElementsByTagName("div")[0].setAttribute("class", "scoreboard-video-outer-link");
link.appendChild(videoWrapper);

var videoThumbnailWrapper = document.createElement('div');
document.getElementsByTagName("div")[0].setAttribute("class", "scoreboard-video--thumbnail");
 videoWrapper.appendChild(videoThumbnailWrapper);

var videoImage = document.createElement('img');
document.getElementsByTagName("img")[0].setAttribute("src", "url-of-image-from-api");
videoThumbnailWrapper.appendChild(videoImage);

Then I basically repeat that process for all nested HTML elements.

Create A-tag
Create class and href attributes for A-tag
Append class name and url to attributes
Append A-tag to main wrapper
Create DIV
Create class attributes for DIV
Append DIV to newly appended A-tag

I'd greatly appreciate it if you could enlighten me on the best way to do what I'm trying to explain here? Seems like it would get very messy.

回答1:

Here's my answer. It's notated. In order to see the effects in the snippet you'll have to go into your developers console to either inspect the wrapper element or look at your developers console log.

We basically create some helper methods to easily create elements and append them to the DOM - it's really not as hard as it seems. This should also leave you in an easy place to append JSON retrieved Objects as properties to your elements!

Here's a Basic Version to give you the gist of what's happening and how to use it

//create element function

function create(tagName, props) {
  return Object.assign(document.createElement(tagName), (props || {}));
}

//append child function

function ac(p, c) {
  if (c) p.appendChild(c);
  return p;
}

//example: 
//get wrapper div
let mainWrapper = document.getElementById("mainWrapper");

//create link and div
let link = create("a", { href:"google.com" });
let div = create("div", { id: "myDiv" });

//add link as a child to div, add the result to mainWrapper
ac(mainWrapper, ac(div, link));

//create element function

function create(tagName, props) {
  return Object.assign(document.createElement(tagName), (props || {}));
}

//append child function

function ac(p, c) {
  if (c) p.appendChild(c);
  return p;
}

//example: 
//get wrapper div
let mainWrapper = document.getElementById("mainWrapper");

//create link and div
let link = create("a", { href:"google.com", textContent: "this text is a Link in the div" });
let div = create("div", { id: "myDiv", textContent: "this text is in the div! " });

//add link as a child to div, add the result to mainWrapper
ac(mainWrapper, ac(div, link));

div {
border: 3px solid black;
padding: 5px;

}

<div id="mainWrapper"></div>

Here is how to do specifically what you asked with more thoroughly notated code.

//get main wrapper
let mainWrapper = document.getElementById("mainWrapper");

//make a function to easily create elements
//function takes a tagName and an optional object for property values
//using Object.assign we can make tailored elements quickly.

function create(tagName, props) {
  return Object.assign(document.createElement(tagName), (props || {}));
}


//document.appendChild is great except 
//it doesn't offer easy stackability
//The reason for this is that it always returns the appended child element
//we create a function that appends from Parent to Child 
//and returns the compiled element(The Parent).
//Since we are ALWAYS returning the parent(regardles of if the child is specified) 
//we can recursively call this function to great effect
//(you'll see this further down)
function ac(p, c) {
  if (c) p.appendChild(c);
  return p;
}

//these are the elements you wanted to append
//notice how easy it is to make them!

//FYI when adding classes directly to an HTMLElement
//the property to assign a value to is className  -- NOT class
//this is a common mistake, so no big deal!

var link = create("a", {
  className: "scoreboard-video-outer-link",
  url: "google.com"
});

var videoWrapper = create("div", {
  className: "scoreboard-video-outer-link"
});

var videoThumbnailWrapper = create("div", {
  className: "scoreboard-video--thumbnail"
});

var videoImage = create("img", {
  src: "url-of-image-from-api"
});

//here's where the recursion comes in:
ac(mainWrapper, ac(link, ac(videoWrapper, ac(videoThumbnailWrapper, videoImage))));

//keep in mind that it might be easiest to read the ac functions backwards
//the logic is this:

//Append videoImage to videoThumbnailWrapper
//Append (videoImage+videoThumbnailWrapper) to videoWrapper 
//Append (videoWrapper+videoImage+videoThumbnailWrapper) to link
//Append (link+videoWrapper+videoImage+videoThumbnailWrapper) to mainWrapper

let mainWrapper = document.getElementById('mainWrapper');

function create(tagName, props) {
  return Object.assign(document.createElement(tagName), (props || {}));
}

function ac(p, c) {
  if (c) p.appendChild(c);
  return p;
}

var link = create("a", {
  className: "scoreboard-video-outer-link",
  url: "google.com"
});

var videoWrapper = create("div", {
  className: "scoreboard-video-outer-link"
});

var videoThumbnailWrapper = create("div", {
  className: "scoreboard-video--thumbnail"
});



var videoImage = create("img", {
  src: "url-of-image-from-api"
});

ac(mainWrapper, ac(link, ac(videoWrapper, ac(videoThumbnailWrapper, videoImage))));
//pretty fancy.
//This is just to show the output in the log,
//feel free to just open up the developer console and look at the mainWrapper element.

console.dir(mainWrapper);

<div id="mainWrapper"></div>

回答2:

Short version

Markup.js's loops.

Long version

You will find many solutions that work for this problem. But that may not be the point. The point is: is it right? And you may using the wrong tool for the problem.

I've worked with code that did similar things. I did not write it, but I had to work with it. You'll find that code like that quickly becomes very difficult to manage. You may think: "Oh, but I know what it's supposed to do. Once it's done, I won't change it."

Code falls into two categories:

Code you stop using and you therefore don't need to change.
Code you keep using and therefore that you will need to change.

So, "does it work?" is not the right question. There are many questions, but some of them are: "Will I be able to maintain this? Is it easy to read? If I change one part, does it only change the part I need to change or does it also change something else I don't mean to change?"

What I'm getting at here is that you should use a templating library. There are many for JavaScript.

In general, you should use a whole JavaScript application framework. There are three main ones nowadays:

ReactJS
Vue.js
Angular 2

For the sake of honesty, note I don't follow my own advice and still use Angular. (The original, not Angular 2.) But this is a steep learning curve. There are a lot of libraries that also include templating abilities.

But you've obviously got a whole project already set up and you want to just plug in a template into existing JavaScript code. You probably want a template language that does its thing and stays out of the way. When I started, I wanted that too. I used Markup.js . It's small, it's simple and it does what you want in this post.

https://github.com/adammark/Markup.js/

It's a first step. I think its loops feature are what you need. Start with that and work your way to a full framework in time.

回答3:

Take a look at this - [underscore._template] It is very tiny, and useful in this situation. (https://www.npmjs.com/package/underscore.template).

const targetElement = document.querySelector('#target')

// Define your template
const template = UnderscoreTemplate(
'<a class="<%- link.className %>" href="<%- link.url %>">\
  <div class="<%- wrapper.className %>">\
    <div class="<%- thumbnail.className %>">\
      <img src="<%- thumbnail.image %>">\
    </div>\
    <div class="<%- info.className %>">\
      <div class="<%- info.title.className %>"><%- info.title.text %></div>\
    </div>\
  </div>\
</a>');
 
// Define values for template
const obj = {
  link: {
    className: 'scoreboard-video-outer-link',
    url: '#someurl'
  },
  wrapper: {
    className: 'scoreboard-video--wrapper'
  },
  thumbnail: {
    className: 'scoreboard-video--thumbnail',
    image: 'http://via.placeholder.com/350x150'
  },
  info: {
    className: 'scoreboard-video--info',
    title: {
      className: 'scoreboard-video--title',
      text: 'Pelicans @ Bulls Postgame: E`Twaun Moore 10-8-17'
    }
  }
};

// Build template, and set innerHTML to output element.
targetElement.innerHTML = template(obj)

// And of course you can go into forEach loop here like

const arr = [obj, obj, obj]; // Create array from our object
arr.forEach(item => targetElement.innerHTML += template(item))

<script src="https://unpkg.com/underscore.template@0.1.7/dist/underscore.template.js"></script>
<div id="target">qq</div>

来源：https://stackoverflow.com/questions/46738333/using-javascript-loop-to-create-multiple-html-elements

标签

javascript

json

api-design

Using Javascript loop to create multiple HTML elements

问题

回答1:

回答2:

Short version

Long version

回答3: