javascript regex to match date pattern YYYY-MM-DD

regex-yyyy-mm-dd.js

// allows YYYY/M/D and periods instead of slashes
// http://stackoverflow.com/questions/24989065/trying-to-validate-yyyy-mm-dd
/^\d{4}[\/.]\d{1,2}[\/.]\d{1,2}$/

// YYYY-MM-DD and YYYY-M-D
// http://stackoverflow.com/questions/6177975/how-to-validate-date-with-format-mm-dd-yyyy-in-javascript
/^\d{4}\-\d{1,2}\-\d{1,2}$/

// YYYY-MM-DD
// https://gist.github.com/arth2o/8471150
/(\d{4})-(\d{2})-(\d{2})/

/^\d{4}-\d{1,2}-\d{1,2}$/

for what were used escape characters \-?!
it can be changed to:

/^\d{4}-\d{1,2}-\d{1,2}$/