In checkout.liquid, try this. It’s written using jquery but moving it to purely javascript shouldn’t be a problem.
$(async function(){
if(window.location.href.indexOf(`step=shipping_method`)>-1||$(`[data-shipping-method]`).length||$(`title`).text().indexOf(`Shipping`)>-1) {
if ($(`[data-shipping-method]`).length) {
adjustShippingTransitTimes();
return;
}
let kpDSMcount=0;
while (!$(`[data-shipping-method]`).length&&kpDSMcount<100) {
kpDSMcount++;
await sleep(100);
}
if ($(`[data-shipping-method]`).length) {
adjustShippingTransitTimes();
}
}
});
function adjustShippingTransitTimes() {
$(`[data-shipping-method-label-title]`).each(function() {
const thisEl=$(this);
const sEl=thisEl.find(`span.small-text`);
const sText=sEl.text();
if (sText.indexOf(`day`)>-1) {
const textArr=sText.split(` `);
const numDays=textArr[0];
if(isNaN(numDays)) {
return;
}
const newStr=`${numDays} - ${+numDays+2} business days`;
sEl.text(newStr);
}
});
}
async function sleep(ms) {
return new Promise(resolve => setTimeout(resolve, ms));
}
The output looks like this:
