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

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

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)

Update June 2020

ECMAScript 2021 brings Object.fromEntries which does exactly the requirement:

const 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' ] ];
      
const obj = Object.fromEntries(array);
console.log(obj);

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/fromEntries

This will do it:

const 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' ] ];
    
var obj = {};
array.forEach(function(data){
    obj[data[0]] = data[1]
});
console.log(obj);

A more idiomatic approach would be to use Array.prototype.reduce:

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 = arr.reduce(function (o, currentArray) {
  var key = currentArray[0], value = currentArray[1]
  o[key] = value
  return o
}, {})

console.log(obj)
document.write(JSON.stringify(obj).split(',').join(',<br>'))

This is more visually appealing, when done with ES6 (rest parameters) syntax:

let obj = arr.reduce((o, [ key, value ]) => {
    o[key] = value
    return o
}, {})

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

Update June 2020

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