How do I convert array of Objects into one Object in JavaScript?

Question

Tiny ES6 solution can look like:

var arr = [{key:"11", value:"1100"},{key:"22", value:"2200"}];
var object = arr.reduce(
  (obj, item) => Object.assign(obj, { [item.key]: item.value }), {});

console.log(object)

Also, if you use object spread, than it can look like:

var object = arr.reduce((obj, item) => ({...obj, [item.key]: item.value}) ,{});

One more solution that is 99% faster is(tested on jsperf):

var object = arr.reduce((obj, item) => (obj[item.key] = item.value, obj) ,{});

Here we benefit from comma operator, it evaluates all expression before comma and returns a last one(after last comma). So we don't copy obj each time, rather assigning new property to it.

Trying to fix this answer in How do I convert array of Objects into one Object in JavaScript?,

this should do it:

var array = [
    {key:'k1',value:'v1'},
    {key:'k2',value:'v2'},
    {key:'k3',value:'v3'}
];
var mapped = array .map(item => ({ [item.key]: item.value }) );
var newObj = Object.assign({}, ...mapped );
console.log(newObj );

---

One-liner:

var newObj = Object.assign({}, ...(array.map(item => ({ [item.key]: item.value }) )));

You're probably looking for something like this:

// original
var arr = [ 
  {key : '11', value : '1100', $$hashKey : '00X' },
  {key : '22', value : '2200', $$hashKey : '018' }
];

//convert
var result = {};
for (var i = 0; i < arr.length; i++) {
  result[arr[i].key] = arr[i].value;
}

console.log(result);

I like the functional approach to achieve this task:

var arr = [{ key:"11", value:"1100" }, { key:"22", value:"2200" }];
var result = arr.reduce(function(obj,item){
  obj[item.key] = item.value; 
  return obj;
}, {});

Note: Last {} is the initial obj value for reduce function, if you won't provide the initial value the first arr element will be used (which is probably undesirable).

https://jsfiddle.net/GreQ/2xa078da/

Using Object.fromEntries:

const array = [
    { key: "key1", value: "value1" },
    { key: "key2", value: "value2" },
];

const obj = Object.fromEntries(array.map(item => [item.key, item.value]));

console.log(obj);