[javascript] Adding options to select with javascript

I want this javascript to create options from 12 to 100 in a select with id="mainSelect", because I do not want to create all of the option tags manually. Can you give me some pointers? Thanks

function selectOptionCreate() {

  var age = 88;
  line = "";
  for (var i = 0; i < 90; i++) {
    line += "<option>";
    line += age + i;
    line += "</option>";
  }

  return line;
}

The most concise and intuitive way would be:

var selectElement = document.getElementById('ageselect');_x000D_
_x000D_
for (var age = 12; age <= 100; age++) {_x000D_
  selectElement.add(new Option(age));_x000D_
}

Your age: <select id="ageselect"><option value="">Please select</option></select>

You can also differentiate the name and the value or add items at the start of the list with additional parameters to the used functions:
HTMLSelect?Element?.add(item[, before]);
new Option(text, value, defaultSelected, selected);

None of the above solutions worked for me. Append method didn't give error when i tried but it didn't solve my problem. In the end i solved my problem with data property of select2. I used json and got the array and then give it in select2 element initialize. For more detail you can see my answer at below post.

https://stackoverflow.com/a/41297283/4928277

Often you have an array of related records, I find it easy and fairly declarative to fill select this way:

selectEl.innerHTML = array.map(c => '<option value="'+c.id+'">'+c.name+'</option>').join('');

This will replace existing options.
You can use selectEl.insertAdjacentHTML('afterbegin', str); to add them to the top instead.
And selectEl.insertAdjacentHTML('beforeend', str); to add them to the bottom of the list.

IE11 compatible syntax:

array.map(function (c) { return '<option value="'+c.id+'">'+c.name+'</option>'; }).join('');

The one thing I'd avoid is doing DOM operations in a loop to avoid repeated re-renderings of the page.

var firstSelect = document.getElementById('first select elements id'),
    secondSelect = document.getElementById('second select elements id'),
    optionsHTML = [],
    i = 12;

for (; i < 100; i += 1) {
  optionsHTML.push("<option value=\"Age" + i + "\">Age" + i + "</option>";
}

firstSelect.innerHTML = optionsHTML.join('\n');
secondSelect.innerHTML = optionsHTML.join('\n');

Edit: removed the function to show how you can just assign the html you've built up to another select element - thus avoiding the unnecessary looping by repeating the function call.

Here you go:

for ( i = 12; i <= 100; i += 1 ) {
    option = document.createElement( 'option' );
    option.value = option.text = i;
    select.add( option );
}

Live demo: http://jsfiddle.net/mwPb5/

Update: Since you want to reuse this code, here's the function for it:

function initDropdownList( id, min, max ) {
    var select, i, option;

    select = document.getElementById( id );
    for ( i = min; i <= max; i += 1 ) {
        option = document.createElement( 'option' );
        option.value = option.text = i;
        select.add( option );
    }
}

Usage:

initDropdownList( 'mainSelect', 12, 100 );

Live demo: http://jsfiddle.net/mwPb5/1/

I don't recommend doing DOM manipulations inside a loop -- that can get expensive in large datasets. Instead, I would do something like this:

var elMainSelect = document.getElementById('mainSelect');

function selectOptionsCreate() {
  var frag = document.createDocumentFragment(),
    elOption;
  for (var i=12; i<101; ++i) {
    elOption = frag.appendChild(document.createElement('option'));
    elOption.text = i;
  }
  elMainSelect.appendChild(frag);
}

You can read more about DocumentFragment on MDN, but here's the gist of it:

It is used as a light-weight version of Document to store a segment of a document structure comprised of nodes just like a standard document. The key difference is that because the document fragment isn't part of the actual DOM's structure, changes made to the fragment don't affect the document, cause reflow, or incur any performance impact that can occur when changes are made.

When you create a new Option object, there are two parameters to pass: The first is the text you want to appear in the list, and the second the value to be assigned to the option.

var myNewOption = new Option("TheText", "TheValue");

You then simply assign this Option object to an empty array element, for example:

document.theForm.theSelectObject.options[0] = myNewOption;

See: What is the best way to add options to a select from an array with jQuery?

$('#mySelect')
      .append($('<option>', { value : key })
      .text(value));