JSFiddle - React, Tailwind, and code Playground

HTML

<select name="0product_id[]" class="groupSelect" id="groupsel_0" onchange="productbuilder.update(this.value,0);">
    <option value="0" class="notag" id="id0_0">--Select--</option>
    <option class="notag" value="338" id="id0_338"  >Dual Promoter Puromycin Expression Plasmid - pSF-CMV-PGK-Puro  > £114.00</option>
    <option class="notag" value="282" id="id0_282"  >EMCV IRES Puromycin Expression Plasmid - pSF-CMV-EMCV-Puro  > £114.00</option>
    <option class="notag" value="265" id="id0_265"  >FMDV IRES Puromycin Expression Plasmid - pSF-CMV-FMDV-Puro  > £114.00</option>
    <option class="notag" value="101" id="id0_101"  >Puromycin Selection Plasmid - pSF-CMV-Ub-Puro AscI  > £114.00</option>
    <option class="notag" value="105" id="id0_105"  >Puromycin Selection SV40 Ori Plasmid - pSF-CMV-Ub-Puro-SV40 Ori SbfI  > £114.00</option>
    <option class="notag" value="323" id="id0_323"  >Rous Sarcoma Virus Promoter Puromycin Expression Plasmid - pSF-CMV-RSV-Puro  > £114.00</option>
</select>

JavaScript

$( document ).ready(function() {
    $("#groupsel_0").val("105");    
});