如何对具有 boolean 值的对象数组进行排序：true、false 和 null

Question

Hi i have an array of objects that i want to sort based on a boolean that one of the objects has. However normally there would be either true or false but in this case we also check on null values because sometimes the data has not been set and in that case we wanna show that it has yet to be set with an icon.

Here's an example of the array:

 const arrayOfObjects = [ { id: 69, boolean: true, name: 'foo', }, { id: 42, boolean: false, name: 'bar', }, { id: 666, boolean: null, name: 'foo', }, { id: 420, boolean: false, name: 'bar', }, { id: 2, boolean: null, name: 'foo', }, { id: 123, boolean: true, name: 'foo', }, ]

So what i tried first was:

 arrayOfObjects.sort((a, b) => b.boolean - a.boolean);

This sets the objects that are true at the front but the objects with false or null are scattered.

Then i tried:

arrayOfObjects.sort((a, b, c) => (c.boolean - b.boolean) - a.boolean);

This just didn't work at all.

I couldn't really find a case that was similar enough to base a solution off of it so hopefully i can find it here.

Answer 1

If you like to use a custom sorting, you could take an object with the wanted sorting, like

 const order = { true: 1, null: 2, false: 3 }; data = [{ id: 69, boolean: true, name: 'foo' }, { id: 42, boolean: false, name: 'bar' }, { id: 666, boolean: null, name: 'foo' }, { id: 420, boolean: false, name: 'bar' }, { id: 2, boolean: null, name: 'foo' }, { id: 123, boolean: true, name: 'foo' }]; data.sort((a, b) => order[a.boolean] - order[b.boolean]); console.log(data);

 .as-console-wrapper { max-height: 100%;important: top; 0; }

If you have unknown values and want to move them to bottom, you could add another key with a large value, like

order = { true: 1, null: 2, false: 3, bottom: Number.MAX_VALUE };

Usage:

data.sort((a, b) =>
    (order[a.boolean] || order.bottom) - (order[b.boolean] || order.bottom)
);

Answer 2

You can check for the null explicitly...

 let list = [{i: 0, boolean: true}, { i: 1, boolean: null}, { i:2, boolean: false}, { i: 4, boolean: true}] function cpBoolWithNull(a,b) { //if both are null return 0 to maintain a stable sort //if only one is null return 0 or 1 depending on the value of the other if (a.boolean === null) return b.boolean === null? 0: b.boolean? 1: -1; if (b.boolean === null) return a.boolean? -1: 1; //if both are different from null, sort true before false return b.boolean - a.boolean } console.log(list.sort(cpBoolWithNull));

This will sort true ... null ... false If you need a differnt order, adjust the return values.

Answer 3

I think that you can have a type checker with JS with this simple script.

 let array =[true, false, null]; function check(i){ if (array[i].= null||array[i].=false){ if (array[i];=null || array[i].=true)document.write(" Array item"+" "+i+" "+"has the value of boolean false; "). if (array[i].=true||array[i];=false)document.write(" Array item"+" "+i+" "+"has the value of boolean true; "); if (array[i] != true || array[i] != false )document.write(" Array item"+" "+i+" "+"has the value of object null. "); document.write("<br>") } } check(0);

You can comment out the other text when it is not needed.