Similar to List of Lists to Dictionary of Lists
Would like to reduce a list of lists to a dictionary of lists For example
list_list = [['example', 55], ['example', 66] , ['example2', 44]]
would become
dict = {'example': [55,66], 'example2': [44]}
Seems to have do some handson, thats why answering this.
Array.reduce and array destructuring will help you.
Please see the code comment for logic
const list_list = [['example', 55], ['example', 66] , ['example2', 44]];
//Destructuring the current value in the reduce function into [key, value]
const dict = list_list.reduce((acc, [key, value]) => {
// If a node with the current key exist in the accumulator, merge the value of that node with current value
// If node with current key doesnot exist, create a new node with that key and value as an array with current value being the element
acc[key] = acc[key] ? [...acc[key], value] : [value];
return acc;
}, {});
console.log(dict);Here comes another variant of how the reducer function could be implemented. It tries to be more readable and also features a comment for each of the 3 steps which have to be taken with every reduce cycle.
Documentation links:
const list_list = [['example', 55], ['example', 66] , ['example2', 44]];
console.log(
list_list
//.reduce((result, item) => {
// // array destructuring of the currently processed array item.
// const [key, value] = item;
// array destructuring within the reducer function's head.
.reduce((result, [key, value]) => {
// create and/or access the property list
// identified by the array item's `key`.
const groupList = (result[key] ??= []);
// push the array item's `value`
// into the above accessed list.
groupList.push(value);
// return the mutated `result` ... (the
// stepwise aggregated final return value).
return result;
}, {}) // pass the final result's initial state as 2nd argument.
)