I need help converting an array into an object where the keys are based on whether the index of the array is odd or even.
For example:
Input:
["name", "Tom", "age", 20]
Output: {"name": "Tom", "age": 20}
I know this can be achieved using basic JavaScript functions like forEach, map, and filter, but I'm looking for a simpler solution.
I've explored the underscore.js documentation, but couldn't find a suitable method. Is there an easier way to accomplish this task?
Here's my take on it:
Efficient and straightforward loop solution:
const basicArray = ["title", "John", "age", 30];
// Customizing the Array object
Array.prototype.convertToObject = function() {
let result = {};
for(let index = 0; index < this.length; index += 2) {
let key = this[index], value = this[index + 1];
result[key] = value;
}
return result;
}
// Alternatively, as a standalone function
const convertToObject = arr => {
let result = {};
for(let index = 0; index < arr.length; index += 2) {
let key = arr[index], value = arr[index + 1];
result[key] = value;
}
return result;
}
const basicObjectOne = basicArray.convertToObject(); // Using the prototype method
const basicObjectTwo = convertToObject(basicArray); // Utilizing the standalone function
If you want to assign elements to keys based on a condition, you can utilize Array#forEach along with an index check. If the index is odd, then pair the element with the key from the previous item.
var array = ["name", "Tom", "age", 20],
object = {};
array.forEach(function (a, i, aa) {
if (i & 1) {
object[aa[i - 1]] = a;
}
});
console.log(object);You can achieve the same result using Array#reduce.
var array = ["name", "Tom", "age", 20],
object = array.reduce(function (r, a, i, aa) {
if (i & 1) {
r[aa[i - 1]] = a;
}
return r;
}, {});
console.log(object);Code snippet using underscores:
output = _.object(..._.partition(input, (_, i) => !(i % 2)))
The _.partition function divides the input array into two subarrays: one for keys and one for values. We then use _.object to create an object from these key-value pairs.
If you prefer functional and semantic code:
const even = i => !(i % 2);
const index = fn => (_, i) => fn(i);
output = _.object(..._.partition(input, index(even)))
Another approach is the recursive solution:
function arrayToObject([prop, value, ...rest], result = {}) {
return prop ? arrayToObject(rest, Object.assign(result, {[prop]: value})) : result;
}
For those who prefer an iterative method:
function arrayToObject(arr) {
const result = {};
while (arr.length) result[arr.shift()] = arr.shift();
return result;
}
An alternative approach is to utilize the reduce method:
var data = ["name", "Alice", "age", 30],
result = data.reduce((previous, current, index, array) => (index % 2 ? previous[array[index - 1]] = current : previous[current], previous),{});
console.log(result);This particular operation can also be achieved using the reduce function.
let data = ["product", "phone", "price", 500] ;
let result = {}
data.forEach((item, index, array) => {
if (index % 2 === 0) result[item] = array[index+1];
});
console.log(result); //{ product: 'phone', price: 500 }
An example of a for loop with conditional assignment
var elements = ["element1", "value1", "element2", 42, "element3"];
var dictionary = {};
for (var index = 0; index < elements.length; index += 2){
//First iteration: assign dictionary["element1"] to "value1"
//Second iteration: assign dictionary["element2"] to 42
//Third iteration: assign dictionary["element3"] to "" since elements[5] is undefined
dictionary[elements[index]] = elements[index + 1] || "";
}
const array = ["name", "Tom", "age", 20, "address", "London"];
function extractParams([key, value, ...remaining]) {
return key ? { [key]: value, ...extractParams(remaining) } : {};
}
console.log(JSON.stringify(extractParams(array), null, 3));
// For example, in node js to obtain arguments in this way
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