What is the process for using a JavaScript Date object to assign a value to an html input with the type datetime-local?

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Here is the process to use a JavaScript Date object to assign a value to an HTML input with the type datetime-local:

1. Create a new Date object and set the desired date/time values.

var date = new Date();
date.setFullYear(2022);
date.setMonth(0);
date.setDate(31);
date.setHours(12);
date.setMinutes(0);
date.setSeconds(0);

1. Get a reference to the desired HTML input element.

var input = document.getElementById('datetime-input');

1. Format the date/time string in ISO format, which is required by the datetime-local input type.

var dateTimeString = date.toISOString().substring(0, 16);

1. Set the value of the HTML input element to the formatted date/time string.

input.value = dateTimeString;

This will set the value of the input to "2022-01-31T12:00".