I have an array with object, which I need to sort in a such way that first the parent object should appear, and then its children objects, and so on. However, when I try to find index of a parent object in array in order to push the children object after it, the findIndex() method returns -1. Can somebody point to the root of this problem, as I cannot clearly see why it does that. The code and data array that I'm using is written below.
const data = [
{
"_id": "0",
"parent": null,
"title": "All"
}, {
"_id": "61c0a9cb8f67e811d55abb2d",
"parent": null,
"title": "Electronics"
}, {
"_id": "61c0a9cb8f67e811d55abb2e",
"parent": { "_id": "61c0a9cb8f67e811d55abb2d" },
"title": "Phones"
}, {
"_id": "61c0a9cb8f67e811d55abb2f",
"parent": { "_id": "61c0a9cb8f67e811d55abb2d" },
"title": "Laptops"
}, {
"_id": "61c0a9cb8f67e811d55abb30",
"parent": { "_id": "61c0a9cb8f67e811d55abb2d" },
"title": "TVs"
}, {
"_id": "61c0a9cb8f67e811d55abb31",
"parent": null,
"title": "Literature"
}, {
"_id": "61c0a9cb8f67e811d55abb32",
"parent": { "_id": "61c0a9cb8f67e811d55abb31"},
"title": "Study Literature"
}, {
"_id": "61c0a9cb8f67e811d55abb33",
"parent": { "_id": "61c0a9cb8f67e811d55abb31" },
"title": "Fictional Literature"
}, {
"_id": "61c0a9cb8f67e811d55abb34",
"parent": { "_id": "61c0a9cb8f67e811d55abb31" },
"title": "Comic books"
}, {
"_id": "61c0a9cb8f67e811d55abb35",
"parent": { "_id": "61c0a9cb8f67e811d55abb2e" },
"title": "Smartphones"
}, {
"_id": "61c0a9cb8f67e811d55abb36",
"parent": { "_id": "61c0a9cb8f67e811d55abb35" },
"title": "Accessories"
}
];
let parents = [];
data.forEach( element => {
if( element.parent == null ) {
parents.push(element);
}
else {
let parentId = element.parent._id;
let index = parents.findIndex(item => {
item._id == parentId;
});
console.log(index);
parents.splice(index+1, 0, element);
}
});Using item => {parentId == item._id;} does require a 'return' to be used: item => {return parentId == item._id;} without the return the function is basically item => null; which is than seen as false by .findIndex() resulting in a -1
If you use the arrow function without the curly braces a return is implied (But limits you to single line expressions as a trade-off): item => parentId == item._id
Source: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/Arrow_functions