javascript - How to convert an array of key-value tuples into an object

Question

I have an array:

[ [ 'cardType', 'iDEBIT' ],
  [ 'txnAmount', '17.64' ],
  [ 'txnId', '20181' ],
  [ 'txnType', 'Purchase' ],
  [ 'txnDate', '2015/08/13 21:50:04' ],
  [ 'respCode', '0' ],
  [ 'isoCode', '0' ],
  [ 'authCode', '' ],
  [ 'acquirerInvoice', '0' ],
  [ 'message', '' ],
  [ 'isComplete', 'true' ],
  [ 'isTimeout', 'false' ] ]

But I can't access data via an array's key, e.g. arr['txnId'] does not return 20181. How can I convert the above array of tuples into an object, so that I can easily access data by key.

Answer 1

Update 2020: As baao notes, Object.fromEntries(arr) now does this on all modern browsers.

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You can use Object.assign, the spread operator, and destructuring assignment for an approach that uses map instead of @royhowie’s reduce, which may or may not be more intuitive:

Object.assign(...arr.map(([key, val]) => ({[key]: val})))

E.g.:

var arr = [ [ 'cardType', 'iDEBIT' ],
  [ 'txnAmount', '17.64' ],
  [ 'txnId', '20181' ],
  [ 'txnType', 'Purchase' ],
  [ 'txnDate', '2015/08/13 21:50:04' ],
  [ 'respCode', '0' ],
  [ 'isoCode', '0' ],
  [ 'authCode', '' ],
  [ 'acquirerInvoice', '0' ],
  [ 'message', '' ],
  [ 'isComplete', 'true' ],
  [ 'isTimeout', 'false' ] ]

var obj = Object.assign(...arr.map(([key, val]) => ({[key]: val})))

console.log(obj)