I'm trying to sort a string[] in descending way. So far what I have done is the code below:
let values = ["Saab", "Volvo", "BMW"]; // example
values.sort();
values.reverse();
It's working but I'm trying to figure out if there is a better way to do it.
You need to create a comparison function and pass it as a parameter of sort function:
values.sort((one, two) => (one > two ? -1 : 1));
A more current answer is that you can utilize String.prototype.localCompare() to get a numeric comparison value.
Simple example:
let values = ["Saab", "Volvo", "BMW"];
values.sort((a, b) => b.localeCompare(a))
This also won't cause TypeScript warnings as the output of localCompare is a number.
More info and additional function parameters can be seen here: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/localeCompare
values.sort((a, b) => b.localeCompare(a, undefined, {numeric: true}))
a.toUpperCase() > b.toUpperCase() ? -1 : 1, but be careful with very large datasets, localeCompare is about twice slower, even though it still is pretty quick.
Use the following code to sorting the Array in ascending and descending order.
const ascending: any= values.sort((a,b) => (a > b ? 1 : -1));
const descending: any= values.sort((a,b) => (a > b ? -1 : 1))
The most recent lib that I know
https://www.npmjs.com/package/ngx-pipes
const numbers = [2, 1, 3];
const obj = [
{id: 4, name: 'Dave', amount: 2},
{id: 2, name: 'Michael', amount: 2},
{id: 3, name: 'Dan', amount: 1},
{id: 1, name: 'John', amount: 1}
];
const deepObj = [
{id: 1, name: 'John', amount: 1337, deep: {prop: 4}},
{id: 2, name: 'Michael', amount: 42, deep: {prop: 2}},
{id: 3, name: 'Dan', amount: 1, deep: {prop: 1}},
{id: 4, name: 'Dave', amount: 2, deep: {prop: 3}}
];
<!-- Returns array ordered by value -->
<p>{{ numbers | orderBy }}</p> <!-- Output: [1, 2, 3] -->
<p>{{ numbers | orderBy: '-' }}</p> <!-- Output: [3, 2, 1] -->
<!-- Returns array ordered by value of property -->
<p>{{ deepObj | orderBy: 'amount' }}</p>
<!-- Output: [{id: 3, ...}, {id: 4, ...}, {id: 2, ...}, {id: 1, ...}] -->
<p>{{ deepObj | orderBy: '-amount' }}</p>
<!-- Output: [{id: 1, ...}, {id: 2, ...}, {id: 4, ...}, {id: 3, ...}] -->
<!-- Returns array ordered by value of deep property -->
<p>{{ deepObj | orderBy: 'deep.prop' }}</p>
<!-- Output: [{id: 3, ...}, {id: 2, ...}, {id: 4, ...}, {id: 1, ...}] -->
<p>{{ deepObj | orderBy: '-deep.prop' }}</p>
<!-- Output: [{id: 1, ...}, {id: 4, ...}, {id: 2, ...}, {id: 3, ...}] -->
<!-- Returns array ordered by mutliple properties -->
<p>{{ obj | orderBy: ['amount', 'id'] }}</p>
<!-- Output: [{id: 1, ...}, {id: 3, ...}, {id: 2, ...}, {id: 4, ...}] -->
Must be like this programmatically
@Component({
// ..
providers: [OrderByPipe]
})
export class AppComponent {
constructor(private orderByPipe: OrderByPipe){
let values = ["Saab", "Volvo", "BMW"];
this.orderByPipe.transform(values, '-');
}
}
This is normal reverse sorting
var nums:number[] = [1,2,3,4]
nums.sort((a,b)=> a < b ? 1:-1)
[ 4, 3, 2, 1 ]
If you have to do the sorting of custom objects, try this
class Student{
name:String
marks:Number
constructor(name:string, marks:number) {
this.name = name
this.marks = marks
}
}
var students:Array<Student> = [
new Student("aseem",47),
new Student("prem",97),
new Student("john",100)
]
console.log(students.sort( (a,b)=> a.marks > b.marks ? -1:1 ))
would result in sorting by marks in reverse order
/usr/local/bin/node /Users/asee2278/git/mycode/JavaScriptLab/typeScript/concepts/sort.js
[
Student { name: 'john', marks: 100 },
Student { name: 'prem', marks: 97 },
Student { name: 'aseem', marks: 47 }
]
values.sort((a,b) => 0 - (a > b ? 1 : -1));?