var initial = 'dd/mm/yyyy'.split(///);
console.log( [ initial[1], initial[0], initial[2] ].join('/')); //=> 'mm/dd/yyyy'
Edit 2021/05/14: A snippet using ES20xx
const pad = v => v.padStart(2, `0`);
const initialDate= new Date().toLocaleDateString("nl-NL")
.split(/[-/]/).map(pad).join("/");
const toFragments = dateString => initialDate
.split(/[-/]/).map(pad);
const dateTo_mmddyyyy = ([date, month, year], divider = "/") =>
`${month}${divider}${date}${divider}${year}`;
const [date, month, year] = toFragments(initialDate);
console.log( `initial (dd/mm/yyyy): ${initialDate}`);
console.log( `reformatted to mm/dd/yyyy (array join): ${
[month, date, year].join('/') }` );
console.log( `reformatted to mm-dd-yyyy (function): ${
dateTo_mmddyyyy(toFragments(initialDate), "-") }` );
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