Convert an arrays of array surrounded by quotes into string array

user_5866599 0
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I have date duration values in following format.

array1 = '[["2022-01-18","2022-01-21"],["2022-02-15","2022-02-17"], ...]';

And need to convert it as follows,

array2 = [ '2022-01-18 - 2022-01-21', '2022-02-15 - 2022-02-17', ... ]

For the work done I have followed two ways,

  1. formattedArray1 = array1.replace(/","/g, " - ").reduce((a, b) => a.concat(b), [])

this gives me an error:

array2.reduce is not a function

  1. formattedArray2 = [].concat.apply([], array1.replace(/","/g, " - ")); and this gives me the error

CreateListFromArrayLike called on non-object

To fix this any thought would be highly appreciated!

arrays json javascript
4 Answers

What you've got there is an array serialised to JSON.

You can parse it to an array then map it to the value you want

const array1 = '[["2022-01-18","2022-01-21"],["2022-02-15","2022-02-17"]]';

const arr = JSON.parse(array1);
const array2 = arr.map(([from, to]) => `${from} - ${to}`);
console.log(array2);

If you're curious (like I was) about the performance of the template literal vs Array.prototype.join(), the results from https://jsbench.me are below...

Template literal

2678.21 ops/s ± 0.85%
Fastest

Array.prototype.join()

1150.62 ops/s ± 0.51%
57.04 % slower

benchmark results

user_2833660

array1 is stored as String, so you need to convert it to Array to use reduce or other array methods.

array1 = '[["2022-01-18","2022-01-21"],["2022-02-15","2022-02-17"]]';
arr = JSON.parse(array1)
formattedArray1 = arr.map((e) => e.join(" - "))
// ['2022-01-18 - 2022-01-21', '2022-02-15 - 2022-02-17']
user_115661610
  1. You are calling reduce on type string( array1.replace(/","/g, " - ") will return a string) , reduce works only with Array.prototype that's why you are getting reduce is not a function.

array2.reduce is not a function error.

You need to parse the array before doing reduce.

const array1 = '[["2022-01-18","2022-01-21"],["2022-02-15","2022-02-17"]]';
const parsedArr = JSON.parse(array1);
const result = parsedArr.map(date => date.join(" - ") )
console.log(result)

user_179489480

Another Alternative

The transform could also be done at the same time the json is parsed by providing a reviver function that evaluates each key-value. if the value is a child array then join the elements.

let json = '[["2022-01-18","2022-01-21"],["2022-02-15","2022-02-17"]]';


let data = JSON.parse(json, (k,v) => k && v.push ? v.join(" - ") : v );


console.log(data);

user_9434350
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