Get yesterday - format: yyyy-mm-dd

yesterday.js

function yesterday() {
	'use strict';
	
	var date = new Date();

	function formatNumberTo2Digits(number) {
		return ('0' + (number)).slice(-2);
	}
	
	// magic
	date.setDate(date.getDate() - 1);

	var year = date.getFullYear();
	var month = formatNumberTo2Digits(date.getUTCMonth() + 1);
	var day = formatNumberTo2Digits(date.getUTCDate());

	return year + '-' + month + '-' + day;
}

yesterday_es6.js

function yesterday(timestamp) {
	'use strict'
	
	const date = new Date(timestamp)

	date.setDate(date.getDate() - 1)
	
	const formatNumberTo2Digits = (number) => ('0' + (number)).slice(-2)
	const year = date.getFullYear()
	const month = formatNumberTo2Digits(date.getUTCMonth() + 1)
	const day = formatNumberTo2Digits(date.getUTCDate())

	return year + '-' + month + '-' + day
}

// Uses:

yesterday(new Date()) // '2018-05-03'
yesterday('2018-05-04T17:07:54.467Z') // '2018-05-03'
yesterday('Tue 01-01-2009 6:00') // '2008-12-31'