如何从 dropdwon 创建所选选项的列表

Question

I am trying to loop through a multiple select dropdown list and add all of the selected options to a comma separated list.

My dropdown code is:

<select name="testnameID" id="testnameID" multiple>
  <option value="1">Test number 1</option>
  <option value="2">Test number 2</option>
  <option value="3">Test number 3</option>
  <option value="4">Test number 4</option>
  <option value="5">Test number 5</option>
<select>

In my tag I am using the following, but think it can be simplified or improved:

var testnameID = $('#testnameID').val();
var testnameText;            
Array.from(document.querySelector("#testnameID").options).forEach(function(option_element) {
            let option_text = option_element.text;
            let is_option_selected = option_element.selected;

            if (is_option_selected===true){
                testnameText = testnameText + option_text +", ";
                console.log("TestnameText: "+testnameText);
                console.log("\n\r");
            }
            
        });

I need to generate a variable, testnameText, which if the first three items were selected, would return a value of "Test number 1, Test number 2, Test number 3"

I'm getting myself in a muddle!

Answer 1

You can try using Document.querySelectorAll() to target all the selected options like the following way:

 Array.from(document.querySelectorAll("#testnameID option:checked")).forEach(function(option_element) { let option_text = option_element.text; var testnameText = option_text +", "; console.log("TestnameText: "+testnameText); console.log("\n\r"); });

 <select name="testnameID" id="testnameID" multiple> <option value="1" selected>Test number 1</option> <option value="2" selected>Test number 2</option> <option value="3" selected>Test number 3</option> <option value="4">Test number 4</option> <option value="5">Test number 5</option> <select>

You can also try using Array.prototype.map() and Arrow function expressions which is more shorter.

The following example creates an array of the selected options:

 var checkedOptions = Array.from(document.querySelectorAll("#testnameID option:checked")); var res = checkedOptions.map(option_element => ("TestnameText: "+option_element.text)); console.log(res);

 <select name="testnameID" id="testnameID" multiple> <option value="1" selected>Test number 1</option> <option value="2" selected>Test number 2</option> <option value="3" selected>Test number 3</option> <option value="4">Test number 4</option> <option value="5">Test number 5</option> <select>

Answer 2

In this case, jquery's each() can help. So getting selected options is pretty simple:

 $('#testnameID:selected').each(function (index, el) { console.log("TestnameText: " + $(el).text()); });

 <script src="https://code.jquery.com/jquery-3.5.1.min.js" integrity="sha256-9/aliU8dGd2tb6OSsuzixeV4y/faTqgFtohetphbbj0=" crossorigin="anonymous"></script> <select name="testnameID" id="testnameID" multiple> <option value="1" selected>Test number 1</option> <option value="2" selected>Test number 2</option> <option value="3" selected>Test number 3</option> <option value="4">Test number 4</option> <option value="5">Test number 5</option> </select>

Answer 3

selectedOptions contains all the selected options of a select element. You can use it like this:

 const select = document.querySelector('select'); select.addEventListener('change', e => { // Option texts as an array const texts = Array.from(e.target.selectedOptions).map(({text}) => text); // Option texts as a comma-separated string const textsStr = texts.join(', '); console.log(texts); console.log(textsStr); });

 <select multiple> <option value="1">Test number 1</option> <option value="2">Test number 2</option> <option value="3">Test number 3</option> <option value="4">Test number 4</option> <option value="5">Test number 5</option> </select>

This works outside of the event too, just refer the select element directly instead of e.target .