Get value from array based on user input in jQuery

Question

I have an array with the alphabet, each letter has a URL attached with it. I also have a list of buttons, each corresponding to a letter of the alphabet.

I want to retrieve the value from the array (url) based on which button the user clicks, the user may click multiple buttons.

So if the user click the button "C", I want to get to retrieve the URL associated with the letter "C" from the array.

I was able to loop through the #letters element's children and get the id of each button. I thought about comparing it against the array somehow but I got lost along the way.

I really have no solution in sight.

HTML

<div class="col-md-12" id="letters">
   <a href="#" class="btn btn-primary" id="A">A</a>
   <a href="#" class="btn btn-primary" id="B">B</a>
   <a href="#" class="btn btn-primary" id="C">C</a>
</div>

Javascript

$(function() {
    let array = {
        'A' : 'http://example.com/A.png',
        'B' : 'http://example.com/B.png',
        'C' : 'http://example.com/C.png',
    };

    $.each(array, function(key, value) {
        console.log('Initializing...', key + ' => ' + value);
    });

    let letters = $('#letters');
    $.each(letters.children(), function(i) {
        console.log(letters.children()[i].id); // get value of id tag
    });
});

Junius L · Accepted Answer · 2019-05-19 21:14:27Z

Use data-* attribute and add event listener to your letters, on click get the clicked item and get the letter using .data().

$(function() {
    let array = {
        'A' : 'https://images.pexels.com/photos/67636/rose-blue-flower-rose-blooms-67636.jpeg?cs=srgb&dl=beauty-bloom-blue-67636.jpg&fm=jpg',
        'B' : 'https://images.pexels.com/photos/1308881/pexels-photo-1308881.jpeg?cs=srgb&dl=ao-dai-beautiful-beauty-1308881.jpg&fm=jpg',
        'C' : 'https://images.pexels.com/photos/237018/pexels-photo-237018.jpeg?cs=srgb&dl=asphalt-beauty-colorful-237018.jpg&fm=jpg',
    };
  
  $('.btn-primary').on('click', function() {
    
    const letter = $(this).data('letter');

    $('#demo').attr('src', array[letter]);
  });
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
  <div class="col-md-12" id="letters">
   <a href="#" data-letter="A" class="btn btn-primary" id="A">A</a>
   <a href="#" data-letter="B" class="btn btn-primary" id="B">B</a>
   <a href="#" data-letter="C" class="btn btn-primary" id="C">C</a>
</div>
  <img width="300" id="demo" src="" />

Ramon Portela · Accepted Answer · 2019-05-19 21:08:59Z

Here is a snippet that I get all the links and attach a click event on then, that simply logs the value which the key corresponds to the clicked button id

(function(){
    let array = {
        'A' : 'http://example.com/A.png',
        'B' : 'http://example.com/B.png',
        'C' : 'http://example.com/C.png',
    };
    
    const buttons = document.querySelectorAll('#letters a');
    buttons.forEach(button => {
      button.addEventListener('click', (e) => console.log(array[e.target.id]));
    });
})();

<div class="col-md-12" id="letters">
   <a href="#" class="btn btn-primary" id="A">A</a>
   <a href="#" class="btn btn-primary" id="B">B</a>
   <a href="#" class="btn btn-primary" id="C">C</a>
</div>

zer00ne · Accepted Answer · 2019-05-20 01:31:21Z

There's no point in writing links in HTML if you plan on having more in the future. Save yourself some time and generate them dynamically. Provided below is a reusable function listLnx() that will generate <a> in HTML from a given list of nearly an unlimited amount of urls. Full details are commented in demo.

// An Array of Arrays each sub-array has a key/value pair
let urls = [
  ['A', 'https://example.com/'],
  ['B', 'https://stackoverflow.com'],
  ['D', 'https://stackoverflow.com/users/2813224/zer00ne'],
  ['C', 'https://css-tricks.com'],
];

/*** listLnx()
1st Param: [Array] (see above)
2nd Param: [String] (optional--default: "body") the tag in which the links 
           will be nested within
*/
/*
*A - Reference the parent tag
*B - Instantiate  Map Object from the array. Array is 
     reversed because the links are prepended to parent
*C - Iterate through map with a for...of loop. The       
     entries() method returns an array of key/value pairs
     which is destructured for easy access
*D - An <a> is created with .createElement() method. The 
     remaining statements assemble each link with the
     following: 
     1. an #id
     2. a [href]
     3. text of #id and hostname
     4. block level style
     5. then prepended to parent tag
*/
const listLnx = (array, selector = `body`) => {
  let node = document.querySelector(selector); //A
  let map = new Map(array.reverse()); //B

  for (const [key, url] of map.entries()) { //C
    const a = document.createElement('a'); //D 
    a.id = key; //1
    a.href = url; //2
    a.textContent = `${key} - ${a.hostname}`; //3
    a.style.display = 'block'; //4
    node.prepend(a); //5
  }
}

listLnx(urls);

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