To get duplicate values from an array with JavaScript Lodash, we can use the filter and includes methods.
For instance, we write
const dups = _.filter(arr, (val, i, iteratee) =>
_.includes(iteratee, val, i + 1)
);
to call filter with arr and a callback that calls includes to check if val is included in the arr array itself from index i + 1 and oin.
iteratee is the arr array.
An array with the duplicates is returned.
To convert a multidimensional JavaScript array to JSON, we use the JSON.stringify method.
For instance, we write
const arr = [
[1, 2, 3],
[4, 5, 6],
];
const json = JSON.stringify(arr);
to call JSON.stringify with arr multidimensional array to convert arr into a JSON string.
To filter JSON by key value with JavaScript, we use the filter method.
For instance, we write
const arr = [
{ time: "2016-07-26 09:02:27", type: "aa" },
{ time: "2016-04-21 20:35:07", type: "ae" },
{ time: "2016-08-20 03:31:57", type: "ar" },
{ time: "2017-01-19 22:58:06", type: "ae" },
{ time: "2016-08-28 10:19:27", type: "ae" },
{ time: "2016-12-06 10:36:22", type: "ar" },
{ time: "2016-07-09 12:14:03", type: "ar" },
{ time: "2016-10-25 05:05:37", type: "ae" },
{ time: "2016-06-05 07:57:18", type: "ae" },
{ time: "2016-10-08 22:03:03", type: "aa" },
{ time: "2016-08-13 21:27:37", type: "ae" },
{ time: "2016-04-09 07:36:16", type: "ar" },
{ time: "2016-12-30 17:20:08", type: "aa" },
{ time: "2016-03-11 17:31:46", type: "aa" },
{ time: "2016-05-04 14:08:25", type: "ar" },
{ time: "2016-11-29 05:21:02", type: "ar" },
{ time: "2016-03-08 05:46:01", type: "ar" },
];
const filtered = arr.filter((a) => a.type == "ar");
to call arr.filter with a callback that checks if thge type property in each object in arr is equal to 'ar'.
An array with the objects in arr with the type property equal to 'ar' is returned.
To do the opposite of includes with JavaScript arrays, we negate the return value of includes.
For instance, we write
const res = filteredResult.filter((e) => !e.selectedFields.includes("Red"));
to call filter with a callback that checks if object e‘s selectedFields property in filteredResult being looped through doesn’t include 'Red'.
To convert array into string without comma and separated by space in JavaScript without concatenation, we call the join method.
For instance, we write
const str = array.join(" ");
to call array.join with a space as the separator to return a string with the items in array joined together.